Pin Configuration appears at end of data sheet.
General Description
The MAX5098A is a dual-output, high-switching-
frequency DC-DC converter with integrated n-channel
switches that can be used either in high-side or low-
side configuration. Each output can be configured either
as a buck converter or a boost converter. In the buck
configuration, this device delivers up to 2A from
converter 1 and 1A from converter 2. The MAX5098A also
integrates a load-dump protection circuitry that is capable
of handling load-dump transients up to 80V for industrial
applications. The load-dump protection circuit utilizes
an internal charge pump to drive the gate of an external
n-channel MOSFET. When an overvoltage or load-dump
condition occurs, the series protection MOSFET absorbs
the high-voltage transient to prevent damage to lower-
voltage components.
The DC-DC converters operate over a wide operating
voltage range from 4.5V to 19V. The MAX5098A operates
180° out-of-phase with an adjustable switching frequency
to minimize external components while allowing the ability
to make trade-offs between the size, efficiency, and cost.
This device utilizes voltage-mode control for stable
operation and external compensation; thus, the loop gain
is tailored to optimize component selection and transient
response. This device can be synchronized to an external
clock fed at the SYNC input. Also, a clock output (CKO)
allows a master-slave connection of two devices with a
four-phase synchronized switching sequence. Additional
features include internal digital soft-start, individual enable
for each DC-DC regulator (EN1 and EN2), open-drain
power-good outputs (PGOOD1 and PGOOD2), and a
shutdown input (ON/OFF).
Other features of the MAX5098A include overvolt-
age protection, short-circuit (hiccup current limit), and
thermal protection. The MAX5098A is available in
a thermally enhanced, exposed pad, 5mm x 5mm,
32-pin TQFN package and is fully specified over the
-40°C to +125°C temperature range.
Applications
●Industrial
Features
●Wide 4.5V to 5.5V or 5.2V to 19V Input Voltage
Range (with Up to 80V Load-Dump Protection)
●Dual-Output DC-DC Converter with Integrated Power
MOSFETs
●Each Output Configurable in Buck or Boost Mode
●Adjustable Outputs from 0.8V to 0.85VIN Buck
Configuration) and from VIN to 28V (Boost
Configuration)
●IOUT1 and IOUT2 of 2A and 1A (Respectively) in
Buck Configuration
●Switching Frequency Programmable from 200kHz to
2.2MHz
●Synchronization Input (SYNC)
●Clock Output (CKO) for Four-Phase Master-Slave
Operation
●Individual Converter Enable Input and Power-Good
Output
●Low-IQ (7µA) Standby Current (ON/OFF)
●Internal Digital Soft-Start and Soft-Stop
●Short-Circuit Protection on Outputs and Maximum
Duty-Cycle Limit
●Overvoltage Protection on Outputs with Auto Restart
●Thermal Shutdown
●Thermally Enhanced 32-Pin TQFN Package
Dissipates Up to 2.7W at +70°C
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
PART TEMP RANGE PIN-PACKAGE
MAX5098AATJ+ -40°C to +125°C 32 TQFN-EP*
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
19-4111; Rev 1; 10/14
Ordering Information
EVALUATION KIT AVAILABLE
V+ to SGND ..........................................................-0.3V to +25V
V+ to IN_HIGH .........................................................-19V to +6V
IN_HIGH to SGND ................................................-0.3V to +19V
IN_HIGH Maximum Input Current ......................................60mA
BYPASS to SGND ................................................-0.3V to +2.5V
GATE to V+ ...........................................................-0.3V to +12V
GATE to SGND .....................................................-0.3V to +36V
SGND to PGND_..................................................-0.3V to +0.3V
VL to SGND ................-0.3V to the Lower of +6V or (V+ + 0.3V)
VDRV to SGND .......................................................-0.3V to +6V
BST1/VDD1, BST2/VDD2, DRAIN_,
PGOOD_ to SGND ............................................ -0.3V to +30V
ON/OFF to SGND .............................-0.3V to (IN_HIGH + 0.3V)
BST1/VDD1 to SOURCE1,
BST2/VDD2 to SOURCE2...................................-0.3V to +6V
SOURCE_ to SGND..............................................-0.6V to +25V
SOURCE_ to PGND_.............................................. -1V for 50ns
EN_ to SGND ..........................................................-0.3V to +6V
OSC, FSEL_1, COMP_, SYNC,
FB_ to SGND........................................... -0.3V to (VL + 0.3V)
CKO to SGND ....................................... -0.3V to (VDRV + 0.3V)
SOURCE1, DRAIN1 Peak Current ............................5A for 1ms
SOURCE2, DRAIN2 Peak Current ............................3A for 1ms
VL, BYPASS to
SGND Short Circuit ................ Continuous, Internally Limited
Continuous Power Dissipation (TA = +70°C)
32-Pin TQFN-EP (derate 34.5mW/°C above +70°C) ...2759mW
Operating Temperature Range ......................... -40°C to +125°C
Storage Temperature Range ........................... -65°C to +150°C
Junction Temperature ...................................................... +150°C
Lead Temperature (soldering, 10s) ................................+300°C
(VDRV = VL, V+ = VL = IN_HIGH = 5.2V or V+ = IN_HIGH = 5.2V to 19V, EN_ = VL, SYNC = GND, IVL = 0mA, PGND_ = SGND,
CBYPASS = 0.22µF (low ESR), CVL = 4.7µF (ceramic), CV+ = 1µF (low ESR), CIN_HIGH = 1µF (ceramic), RIN_HIGH = 3.9kΩ, ROSC = 10kΩ,
TJ = -40°C to +125°C, unless otherwise noted.) (Note 2)
Note 1: Package thermal resistances were obtained using the method described in JEDEC specifications. For detailed information
on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SYSTEM SPECIFICATIONS
Input Voltage Range V+ V+ = IN_HIGH 5.2 19 V
VL = V+ = IN_HIGH (Note 3) 4.5 5.5
V+ Operating Supply Current IQVL unloaded, no switching 4.2 mA
V+ Standby Supply Current IV+STBY VEN_ = 0V, PGOOD_ unconnected, V+ =
VIN_HIGH = 14V 0.75 1.1 mA
Efficiency h
(VOUT1 = 5V at 1.5A,
VOUT2 = 3.3V at 0.75A,
fSW = 1.85MHz
V+ = VL = 5.2V 78
%V+ = 12V 76
V+ = 16V 70
OVERVOLTAGE PROTECTOR
IN_HIGH Clamp Voltage IN_HIGH ISINK = 10mA 19 20 21 V
IN_HIGH Clamp Load
Regulation 1mA < ISINK < 50mA 160 mV
IN_HIGH Supply Current IIN_HIGH VEN_ = VPGOOD_ = VGATE = 0V,
VIN_HIGH = VON/OFF = 14V 270 600 µA
www.maximintegrated.com Maxim Integrated
│
2
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Electrical Characteristics
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Absolute Maximum Ratings
Package Thermal Characteristics (Note 1)
Junction-to-Ambient Thermal Resistance (θJA) ...........29.0°C/W
Junction-to-Case Thermal Resistance (θJC) ..................1.7°C/W
(VDRV = VL, V+ = VL = IN_HIGH = 5.2V or V+ = IN_HIGH = 5.2V to 19V, EN_ = VL, SYNC = GND, IVL = 0mA, PGND_ = SGND,
CBYPASS = 0.22µF (low ESR), CVL = 4.7µF (ceramic), CV+ = 1µF (low ESR), CIN_HIGH = 1µF (ceramic), RIN_HIGH = 3.9kΩ, ROSC = 10kΩ,
TJ = -40°C to +125°C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
IN_HIGH Standby Supply
Current IIN_HIGHSTBY
VON/OFF = 0V, PGOOD_ = V+ =
unconnected, VIN_HIGH = 14V, TA = -40°C
to +85°C
7 9 µA
V+ to IN_HIGH Overvoltage
Clamp VOV VOV = V+ - VIN_HIGH, IGATE = 0mA
(sinking) 1.2 1.85 2.5 V
IN_HIGH Startup Voltage IN_HIGH
UVLO
Rising, ON/OFF = IN_HIGH, GATE rising 3.6 4.1 V
Falling, ON/OFF = IN_HIGH, GATE falling 3.45
GATE Charge Current IGATE_CH VIN_HIGH = VON/OFF = 14V,
VGATE = V+ = 0V 20 45 80 µA
GATE Output Voltage VGATE –
VIN_HIGH
V+ = VIN_HIGH = VON/OFF = 4.5V,
IGATE = 1µA, sourcing 4.0 5.3 7.5
V
V+ = VIN_HIGH = VON/OFF = 14V,
IGATE = 1µA, sourcing 9
GATE Turn-Off Pulldown
Current IGATE_PD VIN_HIGH = 14V, VON/OFF = 0V, V+ = 0V,
VGATE = 5V, sinking 3.6 mA
STARTUP/VL REGULATOR
VL Undervoltage Lockout Trip
Level UVLO VL falling 3.9 4.1 4.3 V
VL Undervoltage Lockout
Hysteresis 180 mV
VL Output Voltage VLISOURCE_ = 0 to 40mA, 5.5V ≤ V+ ≤ 19V 5.0 5.2 5.5 V
VL LDO Short-Circuit Current IVL_SHORT V+ = VIN_HIGH = 5.2V 130 mA
VL LDO Dropout Voltage VLDO ISOURCE_ = 40mA, V+ = VIN_HIGH = 4.5V 300 550 mV
BYPASS OUTPUT
BYPASS Voltage VBYPASS IBYPASS = 0µA 1.98 2.00 2.02 V
BYPASS Load Regulation ∆VBYPASS 0 < IBYPASS < 100µA (sourcing) 2 5 mV
SOFT-START/SOFT-STOP
Digital Ramp Period Soft-
Start/Soft-Stop Internal 6-bit DAC 2048
fSW
Clock
Cycles
Soft-Start/Soft-Stop 64 Steps
VOLTAGE-ERROR AMPLIFIER
FB_ Input Bias Current IFB_ 250 nA
FB_ Input Voltage Set Point VFB_ -40°C ≤ TA ≤ +85°C 0.783 0.8 0.809 V
-40°C ≤ TA ≤ +125°C 0.785 0.814
FB_ to COMP_
Transconductance gM 1.4 2.4 3.4 mS
www.maximintegrated.com Maxim Integrated
│
3
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Electrical Characteristics (continued)
(VDRV = VL, V+ = VL = IN_HIGH = 5.2V or V+ = IN_HIGH = 5.2V to 19V, EN_ = VL, SYNC = GND, IVL = 0mA, PGND_ = SGND,
CBYPASS = 0.22µF (low ESR), CVL = 4.7µF (ceramic), CV+ = 1µF (low ESR), CIN_HIGH = 1µF (ceramic), RIN_HIGH = 3.9kΩ, ROSC = 10kΩ,
TJ = -40°C to +125°C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
INTERNAL MOSFETs
On-Resistance High-Side
MOSFET Converter 1 RON1
ISWITCH = 100mA, BST1/VDD1 to
VSOURCE1 = 5.2V 195
mΩ
ISWITCH = 100mA, BST1/VDD1 to
VSOURCE1 = 4.5V 208 355
On-Resistance High-Side
MOSFET Converter 2 RON2
ISWITCH = 100mA, BST2/VDD2 to
VSOURCE2 = 5.2V 280
mΩ
ISWITCH = 100mA, BST2/VDD2 to
VSOURCE2 = 4.5V 300 520
Minimum Converter 1 Output
Current IOUT1 VOUT1 = 5V, V+ = 12V (Note 4) 2 A
Minimum Converter 2 Output
Current IOUT2 VOUT2 = 3.3V, V+ = 12V (Note 4) 1 A
Converter 1/Converter 2
MOSFET DRAIN_ Leakage
Current
ILK12 VEN1 = VEN2 = 0V, VDRAIN_ = 19V,
VSOURCE_ = 0V 20 µA
Internal Weak Low-Side Switch
On-Resistance RONLSSW_ILSSW = 30mA 22 Ω
INTERNAL SWITCH CURRENT LIMIT
Internal Switch Current-Limit
Converter 1 ICL1 V+ = VIN_HIGH = 5.2V, VL = VDRV =
VBST_/VDD_ = 5.2V 2.8 3.45 4.3 A
Internal Switch Current-Limit
Converter 2 ICL2 V+ = VIN_HIGH = 5.2V, VL = VDRV =
VBST_/VDD_ = 5.2V 1.75 2.1 2.6 A
SWITCHING FREQUENCY
PWM Maximum Duty Cycle DMAX SYNC = SGND, fSW = 1.25MHz 82 90 95 %
Switching Frequency Range fSW 200 2200 kHz
Switching Frequency fSW ROSC = 6.81kΩ, each converter
(FSEL_1 = VL)1.7 1.9 2.1 MHz
Switching Frequency Accuracy 5.6kΩ < ROSC < 10kΩ, 1% 5 %
10kΩ < ROSC < 62.5kΩ, 1% 7
SYNC Frequency Range fSYNC
SYNC input frequency is twice the
individual converter frequency,
FSEL_1 = VL (see the Setting the
Switching Frequency section)
400 4400 kHz
SYNC High Threshold VSYNCH 2 V
SYNC Low Threshold VSYNCL 0.8 V
SYNC Input Leakage ISYNC_LEAK 2 µA
SYNC Input Minimum Pulse
Width tSYNCIN 100 ns
www.maximintegrated.com Maxim Integrated
│
4
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Electrical Characteristics (continued)
Note 2: 100% tested at TA = +25°C and TA = +125°C. Specifications at TA = -40°C are guaranteed by design and not production
tested.
Note 3: Operating supply range (V+) is guaranteed by VL line regulation test. Connect V+ to IN_HIGH and VL for 5V operation.
Note 4: Output current is limited by the power dissipation of the package; see the Power Dissipation section in the Applications
Information section.
(VDRV = VL, V+ = VL = IN_HIGH = 5.2V or V+ = IN_HIGH = 5.2V to 19V, EN_ = VL, SYNC = GND, IVL = 0mA, PGND_ = SGND,
CBYPASS = 0.22µF (low ESR), CVL = 4.7µF (ceramic), CV+ = 1µF (low ESR), CIN_HIGH = 1µF (ceramic), RIN_HIGH = 3.9kΩ, ROSC = 10kΩ,
TJ = -40°C to +125°C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Clock Output Phase Delay CKOPHASE ROSC = 62.5kΩ, with respect to converter
2/SOURCE2 waveform 40 Degrees
SYNC to Source 1 Phase Delay SYNCPHASE ROSC = 62.5kΩ90 Degrees
Clock Output High Level VCKOH VL = 5.2V, sourcing 5mA 3.6 V
Clock Output Low Level VCKOL VL = 5.2V, sinking 5mA 0.6 V
FSEL_1
FSEL_1 Input High Threshold VIH 2 V
FSEL_1 Input Low Threshold VIL 0.8 V
FSEL_1 Input Leakage IFSEL_1_LEAK 2 µA
ON/OFF
ON/OFF Input High Threshold VIH 2 V
ON/OFF Input Low Threshold VIL 0.8 V
ON/OFF Input Leakage Current ION/OFF_LEAK VON/OFF = 5V 0.26 2.00 µA
EN_ INPUTS
EN_ Input High Threshold VIH EN_ rising 1.9 2.0 2.1 V
EN_ Input Hysteresis VEN_HYS 0.5 V
EN_ Input Leakage Current IEN_LEAK -1 +1 µA
POWER-GOOD OUTPUT (PGOOD1, PGOOD2)
PGOOD_ Threshold VTPGOOD_Falling 90 92.5 95 % VFB_
PGOOD_ Output Voltage VPGOOD_ISINK = 3mA 0.4 V
PGOOD_ Output Leakage
Current ILKPGOOD_V+ = VL = VIN_HIGH = VEN_ = 5.2V,
VPGOOD_ = 23V, VFB_ = 1V 2 µA
OUTPUT OVERVOLTAGE PROTECTION
FB_ OVP Threshold Rising VOVP_R107 114 121 % VFB_
FB_ OVP Threshold Falling VOVP_F12.5 V
THERMAL PROTECTION
Thermal Shutdown TSHDN Rising +165 °C
Thermal Hysteresis THYST 20 °C
www.maximintegrated.com Maxim Integrated
│
5
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Electrical Characteristics (continued)
(See the Typical Application Circuit, unless otherwise noted. V+ = VIN_HIGH = 14V, unless otherwise noted. V+ = VIN_HIGH means
that N1 is shorted externally.)
EACH CONVERTER SWITCHING
FREQUENCY vs. TEMPERATURE
MAX5098A toc09
TEMPERATURE (°C)
SWITCHING FREQUENCY (MHz)
-5 30 65 100
1
10
0.1
-40 135
0.3MHz
0.6MHz
1.25MHz
1.85MHz 2.2MHz
FSEL_1 = VL
EACH CONVERTER SWITCHING
FREQUENCY vs. ROSC
MAX5098A toc08
ROSC (kΩ)
SWITCHING FREQUENCY (MHz)
604020
1
080
10
0.1
CONVERTER 1, CONVERTER 2
CONVERTER 1
FSEL_1 = VL,
FSEL_1 = GND,
VL OUTPUT VOLTAGE
vs. CONVERTER SWITCHING FREQUENCY
MAX5098A toc07
CONVERTER SWITCHING FREQUENCY (kHz)
VL OUTPUT VOLTAGE (V)
17001200700
4.2
4.4
4.6
4.8
5.0
5.2
5.4
4.0
200 2200
VIN = 4.5V
VIN = 5.5V VIN = 8V VIN = 19V
VIN = 5V
BOTH CONVERTERS SWITCHING
FSEL_1 = VL
OUTPUT2 VOLTAGE
vs. LOAD CURRENT
MAX5098A toc06
LOAD (A)
OUTPUT2 VOLTAGE (V)
0.90.80.70.60.50.40.3
3.22
3.24
3.26
3.28
3.30
3.20
0.2 1.0
VIN = 5.5V VIN = 16V
VIN = 14V
VOUT = 3.3V
fSW = 1.85MHz
OUTPUT1 VOLTAGE
vs. LOAD CURRENT
MAX5098A toc05
LOAD (A)
OUTPUT1 VOLTAGE (V)
1.81.61.41.21.00.80.60.4
4.92
4.94
4.96
4.98
5.00
4.90
0.2 2.0
VIN = 8V VIN = 14V VIN = 16V
VOUT = 5V
fSW = 1.85MHz
OUTPUT2 EFFICIENCY
vs. LOAD CURRENT
MAX5098A toc04
LOAD (A)
OUTPUT2 EFFICIENCY (%)
0.90.80.6 0.70.4 0.50.30.2 1.0
10
20
30
40
50
60
70
80
90
100
0
VIN = 16V
VIN = 8V
VIN = 14V
VIN = 5.5V
VIN = 4.5V
VOUT = 3.3V
fSW = 300kHz
L2 = 27µH
OUTPUT1 EFFICIENCY
vs. LOAD CURRENT
MAX5098A toc03
LOAD (A)
OUTPUT1 EFFICIENCY (%)
1.81.61.2 1.40.6 0.8 1.00.4
10
20
30
40
50
60
70
80
90
100
0
0.2 2.0
VIN = 8V
VIN = 14V VIN = 16V
VOUT = 5V
fSW = 300kHz
L1 = 18µH
OUTPUT2 EFFICIENCY
vs. LOAD CURRENT
MAX5098A toc02
LOAD (A)
OUTPUT2 EFFICIENCY (%)
0.90.80.6 0.70.4 0.50.30.2 1.0
10
20
30
40
50
60
70
80
90
100
0
VIN = 16V
VIN = 8V
VIN = 14V
VIN = 5.5V
VIN = 4.5V
VOUT = 3.3V
fSW = 1.85MHz
OUTPUT1 EFFICIENCY
vs. LOAD CURRENT
MAX5098A toc01
LOAD (A)
OUTPUT1 EFFICIENCY (%)
1.81.61.2 1.40.6 0.8 1.00.4
10
20
30
40
50
60
70
80
90
100
0
0.2 2.0
VIN = 8V
VIN = 14V VIN = 16V
VOUT = 5V
fSW = 1.85MHz
Maxim Integrated
│
6
www.maximintegrated.com
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Typical Operating Characteristics
(See the Typical Application Circuit, unless otherwise noted. V+ = VIN_HIGH = 14V, unless otherwise noted. V+ = VIN_HIGH means
that N1 is shorted externally.)
OUT-OF-PHASE OPERATION
(FSEL_1 = VL)
MAX5098A toc15
200ns/div
SOURCE2
10V/div
SOURCE1
10V/div
CKO
5V/div
0V
0V
0V
SOFT-START FROM ON/OFF
MAX5098A toc14
2ms/div
VOUT1 = 5V/2A
5V/div
ON/OFF
5V/div
GATE
10V/div
V+
10V/div
VL = EN1 = EN2
5V/div
0V
0V
0V
0V
SOFT-START/SOFT-STOP FROM EN1
MAX5098A toc13
1ms/div
VOUT1 = 5V/2A
5V/div
EN1
5V/div
PGOOD1
5V/div
0V
0V
0V
fSW = 1.85MHz
CONVERTER 2
LOAD-TRANSIENT RESPONSE
MAX5098A toc12
100s/div
VOUT2 = 3.3V
AC-COUPLED
200mV/div
IOUT2
500mA/div
0A
CONVERTER 1
LOAD-TRANSIENT RESPONSE
MAX5098A toc11
100s/div
VOUT1 = 5.0V
AC-COUPLED
200mV/div
IOUT1
1A/div
0A
LINE-TRANSIENT RESPONSE
(BUCK CONVERTER)
MAX5098A toc10
1ms/div
VIN
5V/div
VOUT1 = 5.0V/1.5A
AC-COUPLED
200mV/div
VOUT2 = 3.3V/0.75A
AC-COUPLED
200mV/div
0V
Maxim Integrated
│
7
www.maximintegrated.com
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Typical Operating Characteristics (continued)
(See the Typical Application Circuit, unless otherwise noted. V+ = VIN_HIGH = 14V, unless otherwise noted. V+ = VIN_HIGH means
that N1 is shorted externally.)
FB_ VOLTAGE
vs. TEMPERATURE
MAX5098A toc21
TEMPERATURE (°C)
FB_ VOLTAGE (V)
10065-5 30
0.790
0.795
0.800
0.805
0.815
0.810
0.820
0.825
0.785
-40 135
VL = V+ = VIN_HIGH = 5.5V
OVP BEHAVIOR
MAX5098A toc20
1ms/div
V+
10V/div
GATE
10V/div
VOUT1
10V/div
PGOOD2
10V/div
VOUT2
10V/div
EXTERNAL OVERVOLTAGE REMOVED
0V
0V
0V
0V
0V
FOUR-PHASE OPERATION
(FSEL_1 = VL )
MAX5098A toc19
200ns/div
MASTER SOURCE1
20V/div
MASTER SOURCE2
20V/div
SLAVE SOURCE1
20V/div
SLAVE SOURCE2
20V/div
MASTER
CKO
5V/div
0V
0V
0V
0V
0V
EXTERNAL SYNCHRONIZATION
(FSEL_1 = SGND )
MAX5098A toc18
200ns/div
SOURCE2
10V/div
SOURCE1
10V/div
CKO
5V/div
0V
0V
SYNC
5V/div
0V
0V
EXTERNAL SYNCHRONIZATION
(FSEL_1 = VL)
MAX5098A toc17
200ns/div
SOURCE2
10V/div
SOURCE1
10V/div
CKO
5V/div
0V
0V
SYNC
5V/div
0V
0V
OUT-OF-PHASE OPERATION
(FSEL_1 = SGND)
MAX5098A toc16
200ns/div
SOURCE2
10V/div
SOURCE1
10V/div
CKO
5V/div
0V
0V
0V
Maxim Integrated
│
8
www.maximintegrated.com
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Typical Operating Characteristics (continued)
(See the Typical Application Circuit, unless otherwise noted. V+ = VIN_HIGH = 14V, unless otherwise noted. V+ = VIN_HIGH means
that N1 is shorted externally.)
IN_HIGH STANDBY CURRENT
vs. TEMPERATURE
MAX5098A toc28
TEMPERATURE (°C)
IN_HIGH STANDBY CURRENT (A)
100500
85
95
105
115
125
135
145
75
-50 150
IN_HIGH = 8V
IN_HIGH = 14V
IN_HIGH = 16V
ON/OFF = IN_HIGH
EN1 = EN2 = SGND
IN_HIGH SHUTDOWN CURRENT
vs. TEMPERATURE
MAX5098A toc27
TEMPERATURE (°C)
IN_HIGH SHUTDOWN CURRENT (A)
100500
4
8
12
16
20
0
-50 150
IN_HIGH = 8V
IN_HIGH = 14V
IN_HIGH = 16V
ON/OFF = SGND
V+ STANDBY SUPPLY CURRENT
vs. TEMPERATURE
MAX5098A toc26
TEMPERATURE (°C)
V+ STANDBY SUPPLY CURRENT (mA)
100500
1
2
3
4
0
-50 150
fSW = 1.85MHz
fSW = 300kHz
V+ = IN_HIGH = ON/OFF
EN1 = EN2 = SGND
V+ SWITCHING SUPPLY CURRENT
vs. SWITCHING FREQUENCY
MAX5098A toc25
SWITCHING FREQUENCY (kHz)
V+ SWITCHING SUPPLY CURRENT (mA)
182014401060680
10
20
30
40
50
0
300 2200
TA = +25°C
TA = +135°C
TA = +125°C
TA = +85°C
TA = -40°C
V+ = IN_HIGH = ON/OFF
SOURCE1, SOURCE1 INDICATOR CURRENT,
SOURCE2, SOURCE2 INDICATOR CURRENT
MAX5098A toc24
1s/div
ISOURCE1
500mA/div
NO LOAD
SOURCE1
20V/div
NO LOAD
SOURCE2
20V/div
ISOURCE2
1A/div
0V
0A
0A
0V
BYPASS VOLTAGE
vs. BYPASS CURRENT
MAX5098A toc23
BYPASS CURRENT (µA)
BYPASS VOLTAGE (V)
806020 40
1.992
1.994
1.998
1.996
2.000
1.990
0 100705010 30 90
TA = +25°C
TA = +135°C
TA = +125°C
TA = +85°C
TA = -40°C
BYPASS VOLTAGE
vs. TEMPERATURE
MAX5098A toc22
TEMPERATURE (C)
BYPASS VOLTAGE (V)
10065-5 30
1.994
1.996
1.998
2.000
2.002
2.006
2.004
2.008
2.010
1.990
1.992
-40 135
VL = V+ = VIN_HIGH = 5.5V
Maxim Integrated
│
9
www.maximintegrated.com
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Typical Operating Characteristics (continued)
(See the Typical Application Circuit, unless otherwise noted. V+ = VIN_HIGH = 14V, unless otherwise noted. V+ = VIN_HIGH means
that N1 is shorted externally.)
SYSTEM LOAD-DUMP
MAX5098A toc34
100ms/div
VOUT1
AC-COUPLED
100mV/div
V+
10V/div
GATE
10V/div
IN_HIGH
10V/div
0V
0V
0V
0V
0V
VIN
50V/div
SYSTEM TURN-OFF FROM BATTERY
MAX5098A toc33
10ms/div
VL
10V/div
V+
10V/div
GATE
10V/div
IN_HIGH
10V/div
VIN
10V/div
0V
0V
0V
0V
0V
SYSTEM TURN-ON FROM BATTERY
MAX5098A toc32
10ms/div
VL
10V/div
V+
10V/div
GATE
10V/div
IN_HIGH
10V/div
VIN
10V/div
0V
0V
0V
0V
0V
(VGATE - V) vs. VIN_HIGH
MAX5098A toc31
VIN_HIGH (V)
(VGATE - V) (V)
15.512.08.5
2
4
6
8
10
0
5.0 19.0
TA = +25°C
TA = +135°C
TA = +125°C
TA = +85°C
TA = -40°C
ON/OFF = IN_HIGH
V+ TO IN_HIGH CLAMP VOLTAGE
vs. GATE SINK CURRENT
MAX5098A toc30
GATE SINK CURRENT (mA)
V+ TO IN_HIGH CLAMP VOLTAGE (V)
8642
1
2
3
4
5
0
0 10
TA = +25°C
TA = +135°C
TA = +125°C
TA = +85°C
TA = -40°C
IN_HIGH CLAMP VOLTAGE
vs. CLAMP CURRENT
MAX5098A toc29
CLAMP CURRENT (mA)
IN_HIGH CLAMP VOLTAGE (V)
40302010
20.0
20.1
20.2
20.3
19.9
0 50
TA = +25°C
TA = +135°C
TA = +125°C
TA = +85°C
TA = -40°C
Maxim Integrated
│
10
www.maximintegrated.com
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Typical Operating Characteristics (continued)
PIN NAME FUNCTION
1, 32 SOURCE2 Converter 2 Internal MOSFET Source Connection. For buck converter operation, connect SOURCE2 to
the switched side of the inductor. For boost operation, connect SOURCE2 to PGND_ (Figure 6).
2, 3 DRAIN2
Converter 2 Internal MOSFET Drain Connection. For buck converter operation, use the MOSFET as a high-
side switch and connect DRAIN2 to the DC-DC converters supply input rail. For boost converter operation,
use the MOSFET as a low-side switch and connect DRAIN2 to the inductor and diode junction (Figure 6).
4 PGOOD2 Converter 2 Open-Drain Power-Good Output. PGOOD2 goes low when converter 2’s output falls below 92.5%
of its set regulation voltage. Use PGOOD2 and EN1 to sequence the converters. Converter 2 starts rst.
5 EN2 Converter 2 Active-High Enable Input. Connect to VL for always-on operation.
6 FB2
Converter 2 Feedback Input. Connect FB2 to a resistive divider between converter 2’s output and SGND
to adjust the output voltage. To set the output voltage below 0.8V, connect FB2 to a resistive voltage-
divider from BYPASS to regulator 2’s output (Figure 3). See the Setting the Output Voltage section.
7 COMP2 Converter 2 Internal Transconductance Amplier Output. See the Compensation section.
8 OSC
Oscillator Frequency Set Input. Connect a resistor from OSC to SGND (ROSC) to set the switching
frequency (see the Setting the Switching Frequency section). Set ROSC for an oscillator frequency equal to
the SYNC input frequency when using external synchronization. ROSC is still required when an external
clock is connected to the SYNC input. See the Synchronization (SYNC)/Clock Output (CKO) section.
9 SYNC
External Clock Synchronization Input. Connect SYNC to a 400kHz to 4400kHz clock to synchronize the
switching frequency with the system clock. Each converter frequency is 1/2 of the frequency applied to
SYNC (FSEL_1 = VL). For FSEL_1 = SGND, the switching frequency of converter 1 becomes 1/4 of the
SYNC frequency. Connect SYNC to SGND when not used.
10 GATE
Gate Drive Output. Connect to the gate of the external n-channel load-dump protection MOSFET. GATE =
IN_HIGH + 9V (typ) with IN_HIGH = 12V. GATE pulls to IN_HIGH by an internal n-channel MOSFET when
V+ raises 2V above IN_HIGH. Leave gate unconnected if the load-dump protection is not used (MOSFET not
installed).
11 ON/OFF
n-Channel Switch Enable Input. Drive ON/OFF high for normal operation. Drive ON/OFF low to turn off the
external n-channel load-dump protection MOSFET and reduce the supply current to 7µA (typ). When ON/
OFF is driven low, both DC-DC converters are disabled and the PGOOD_ outputs are driven low. Connect
to V+ if the external load-dump protection is not used (MOSFET not installed).
12 IN_HIGH
Startup Input. IN_HIGH is protected by internally clamping to 21V (max). Connect a resistor (4kΩ max) from
IN_HIGH to the drain of the protection switch. Bypass IN_HIGH with a 4.7µF electrolytic or 1µF minimum
ceramic capacitor. Connect to V+ if the external load-dump protection is not used (MOSFET not installed).
13 V+ Input Supply Voltage. V+ can range from 5.2V to 19V. Connect V+, IN_HIGH, and VL together for 4.5V to
5.5V input operation. Bypass V+ to SGND with a 1µF minimum ceramic capacitor.
14 VL
Internal Regulator Output. The VL regulator is used to supply the drive current at input VDRV. When driving
VDRV, use an RC lowpass lter to decouple switching noise from VDRV to the VL regulator (see the Typical
Application Circuit). Bypass VL to SGND with a 4.7µF minimum ceramic capacitor.
15 SGND Signal Ground. Connect SGND to exposed pad and to the board signal ground plane. Connect the board
signal ground and power ground planes together at a single point.
www.maximintegrated.com Maxim Integrated
│
11
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Pin Description
PIN NAME FUNCTION
16 BYPASS Reference Output Bypass Connection. Bypass to SGND with a 0.22µF or greater ceramic capacitor.
17 FSEL_1
Converter 1 Frequency Select Input. Connect FSEL_1 to VL for normal operation. Connect FSEL_1 to
SGND to reduce converter 1’s switching frequency to 1/2 of converter 2’s switching frequency (Converter 1
switching frequency is 1/4 the CKO frequency). Do not leave FSEL_1 unconnected.
18 COMP1 Converter 1 Internal Transconductance Amplier Output. See the Compensation section.
19 FB1
Converter 1 Feedback Input. Connect FB1 to a resistive divider between converter 1’s output and SGND
to adjust the output voltage. To set the output voltage below 0.8V, connect FB1 to a resistive voltage-
divider from BYPASS to regulator 1’s output (Figure 3). See the Setting the Output Voltage section.
20 EN1 Converter 1 Active-High Enable Input. Connect to VL for an always-on operation.
21 PGOOD1
Converter 1 Open-Drain Power-Good Output. PGOOD1 output goes low when converter 1’s output falls
below 92.5% of its set regulation voltage. Use PGOOD1 and EN2 to sequence the converters. Converter 1
starts rst.
22, 23 DRAIN1
Converter 1 Internal MOSFET Drain Connection. For buck converter operation, use the MOSFET as a high-
side switch and connect DRAIN1 to the DC-DC converters supply input rail. For boost converter operation,
use the MOSFET as a low-side switch and connect DRAIN1 to the inductor and diode junction (Figure 6).
24, 25 SOURCE1 Converter 1 Internal MOSFET Source Connection. For buck operation, connect SOURCE1 to the switched
side of the inductor. For boost operation, connect SOURCE1 to PGND_ (Figure 6).
26 BST1/VDD1
Converter 1 Bootstrap Flying-Capacitor Connection. For buck converter operation, connect BST1/VDD1 to
a 0.1µF ceramic capacitor and diode according to the Typical Application Circuit. For boost converter
Operation, driver bypass capacitor connection. Connect to VDRV and bypass with a 0.1µF ceramic capacitor
to PGND_ (Figure 6).
27 VDRV
Low-Side Driver Supply Input. Connect VDRV to VL through an RC lter to bypass switching noise to the
internal VL regulator. For buck converter operation, connect anode terminals of external bootstrap diodes
to VDRV. For boost converter operation, connect VDRV to BST1/VDD1 and BST2/VDD2. Bypass with a
minimum 2.2µF ceramic capacitor to PGND_ (see the Typical Application Circuit). Do not connect to an
external supply.
28 CKO
Clock Output. CKO is an output with twice the frequency of each converter (FSEL_1 = VL) and 90° out-of-
phase with respect to converter 1. Connect CKO to the SYNC input of another MAX5098A for a four-
phase converter.
29, 30 PGND1,
PGND2 Power Ground. Connect both PGND1 and PGND2 together and to the board power ground plane.
31 BST2/VDD2
Converter 2 Bootstrap Flying-Capacitor Connection. For buck converter operation, connect BST2/VDD2 to
a 0.1µF ceramic capacitor and diode according to the Typical Application Circuit. For boost converter
operation, driver bypass capacitor connection. Connect to VDRV and bypass with a 0.1µF ceramic
capacitor from BST2/VDD2 to PGND_ (Figure 6).
— EP Exposed Pad. Connect EP to SGND. For enhanced thermal dissipation, connect EP to a copper area
as large as possible. Do not use EP as the sole ground connection.
www.maximintegrated.com Maxim Integrated
│
12
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Pin Description (continued)
CONVERTER 1
COMP1
PGOOD1
SOURCE1
DRAIN1
V+
BYPASS
FSEL_1
EN1
SYNC
OSC
VDRV
CKO
EN2
DRAIN2
PGOOD2
CONVERTER 2
VL
CKO2
LDO
Q
S
R
0.2V 0.74V
0.8V
TRANSCONDUCTANCE
ERROR AMPLIFIER
fSW/4
FREQUENCY
CONTROL
PWM
COMPARATOR
CKO1
MAXIMUM DUTY-CYCLE
CONTROL
FB1
VL
VL
BST1/VDD1
IN_HIGH
ON/OFF
0.9V
PGND_
CURRENT
LIMIT
OSCILLATOR
MAIN
OSCILLATOR
GATE
OVERVOLTAGE
OVERVOLTAGE
STARTUP CIRCUIT/
PROTECTION CIRCUIT/
CHARGE PUMP
20V SHUNT
REGULATOR
1.8V
SGND
Q
BST2/VDD2
SOURCE2
FB2
PGND_
COMP2
CHARGE
PUMP
DIGITAL
SOFT-START
FREQUENCY
DIVIDER
MAX5098A
www.maximintegrated.com Maxim Integrated
│
13
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Functional Diagram
Detailed Description
PWM Controller
The MAX5098A dual DC-DC converter uses a
pulse-width-modulation (PWM) voltage-mode control
scheme. On each converter the device includes one inte-
grated n-channel MOSFET switch and requires an external
low-forward-drop Schottky diode for output rectification.
The controller generates the clock signal by dividing down
the internal oscillator (fCKO) or the SYNC input when
driven by an external clock, therefore each controller’s
switching frequency equals half the oscillator frequency
(fSW = fCKO/2) or half of the SYNC input frequency (fSW
= fSYNC/2). An internal transconductance error amplifier
produces an integrated error voltage at COMP_, providing
high DC accuracy. The voltage at COMP_ sets the duty
cycle using a PWM comparator and a ramp generator.
At each rising edge of the clock, converter 1’s MOSFET
switch turns on and remains on until either the appropriate
or maximum duty cycle is reached, or the maximum current
limit for the switch is reached. Converter 2 operates 180°
out-of-phase, so its MOSFET switch turns on at each fall-
ing edge of the clock.
In the case of buck operation (see the Typical Application
Circuit), the internal MOSFET is used in high-side config-
uration. During each MOSFET’s on-time, the associated
inductor current ramps up. During the second half of the
switching cycle, the high-side MOSFET turns off and forward
biases the Schottky rectifier. During this time, the SOURCE_
voltage is clamped to a diode drop (VD) below ground. A
low forward voltage drop (0.4V) Schottky diode must be
used to ensure the SOURCE_ voltage does not go below
-0.6V abs max. The inductor releases the stored energy
as its current ramps down, and provides current to the
output. The bootstrap capacitor is also recharged when the
SOURCE_ voltage goes low during the high-side MOSFET
off-time. The maximum duty-cycle limit ensures proper
bootstrap charging at startup or low input voltages. The
circuit goes in discontinuous conduction mode operation at
light load, when the inductor current completely discharges
before the next cycle commences. Under overload condi-
tions, when the inductor current exceeds the peak current
limit of the respective switch, the high-side MOSFET turns
off quickly and waits until the next clock cycle.
In the case of boost operation, the MOSFET is a low-
side switch (Figure 6). During each on-time, the induc-
tor current ramps up. During the second half of the
switching cycle, the low-side switch turns off and for-
ward biases the Schottky diode. During this time, the
DRAIN_ voltage is clamped to a diode drop (VD) above
VOUT_ and the inductor provides energy to the output
as well as replenishes the output capacitor charge.
ON/OFF
The MAX5098A provides an input (ON/OFF) to turn on and
off the external load-dump protection MOSFET. Drive ON/
OFF high for normal operation. Drive ON/OFF low to turn
off the external n-channel load-dump protection MOSFET
and reduce the supply current to 7µA (typ). When ON/OFF
is driven low, the converter also turns off, and the PGOOD_
outputs are driven low. V+ will be self discharged through
the converters output currents and the IC supply current.
Internal Oscillator/Out-of-Phase Operation
The internal oscillator generates the 180° out-of-phase
clock signal required by each regulator. The switching
frequency of each converter (fSW) is programmable from
200kHz to 2.2MHz using a single 1% resistor at ROSC. See
the Setting the Switching Frequency section.
With dual synchronized out-of-phase operation, the
MAX5098A’s internal MOSFETs turn on 180° out-of-phase.
The instantaneous input current peaks of both regulators
do not overlap, resulting in reduced RMS ripple current and
input-voltage ripple. This reduces the required input capac-
itor ripple current rating, allows for fewer or less expensive
capacitors, and reduces shielding requirements for EMI.
Synchronization (SYNC)/
Clock Output (CKO)
The main oscillator can be synchronized to the system
clock by applying an external clock (fSYNC) at SYNC. The
fSYNC frequency must be twice the required operating
frequency of an individual converter. Use a TTL logic sig-
nal for the external clock with at least 100ns pulse width.
ROSC is still required when using external synchronization.
Program the internal oscillator frequency to have fSW = 1/2
fSYNC. The device is properly synchronized if the SYNC
frequency, fSYNC, varies within ±20%.
Two MAX5098As can be connected in the master-slave
configuration for four ripple-phase operation (Figure 1).
The MAX5098A provides a clock output (CKO) that is 45°
phase-shifted with respect to the internal switch turn-on
edge. Feed the CKO of the master to the SYNC input of the
slave. The effective input ripple switching frequency is four
times the individual converter’s switching frequency. When
driving the master converter using an external clock at
SYNC, set the fSYNC clock duty cycle to 50% for effective
90° phase-shifted interleaved operation. When a SYNC is
applied (and FSEL_1 = 0), converter 1 duty cycle is limited
to 75% (max).
www.maximintegrated.com Maxim Integrated
│
14
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Input Voltage (V+)/
Internal Linear Regulator (VL)
All internal control circuitry operates from an internally
regulated nominal voltage of 5.2V (VL). At higher input
voltages (V+) of 5.2V to 19V, VL is regulated to 5.2V. At
5.2V or below, the internal linear regulator operates in
dropout mode, where VL follows V+. Depending on the
load on VL, the dropout voltage can be high enough to
reduce VL below the undervoltage lockout (UVLO) thresh-
old. Do not use VL to power external circuitry.
For input voltages less than 5.5V, connect V+ and VL
together. The load on VL is proportional to the switching
frequency of converter 1 and converter 2. See the VL
Output Voltage vs. Converter Switching Frequency graph
in the Typical Operating Characteristics. For input voltage
ranges higher than 5.5V, disconnect VL from V+.
Bypass V+ to SGND with a 1µF or greater ceramic capac-
itor placed close to the MAX5098A. Bypass VL with a
4.7µF ceramic capacitor to SGND.
Undervoltage Lockout/
Soft-Start/Soft-Stop
The MAX5098A includes an undervoltage lockout with
hysteresis and a power-on-reset circuit for converter turn-
on and monotonic rise of the output voltage. The falling
UVLO threshold is internally set to 4.1V (typ) with 180mV
hysteresis. Hysteresis at UVLO eliminates “chattering”
during startup. When VL drops below UVLO, the internal
MOSFET switches are turned off.
The MAX5098A digital soft-start reduces input inrush
currents and glitches at the input during turn-on. When
UVLO is cleared and EN_ is high, digital soft-start slowly
ramps up the internal reference voltage in 64 steps. The
total soft-start period is 4096 internal oscillator switching
cycles.
Driving EN_ low initiates digital soft-stop that slowly
ramps down the internal reference voltage in 64 steps.
The total soft-stop period is equal to the soft-start period.
To calculate the soft-start/soft-stop period, use the follow-
ing equation:
SS
CKO
4096
t (ms) f (kHz)
=
where fCKO is the internal oscillator and fCKO is twice
each converters’ switching frequency (FSEL_1 = VL).
Enable (EN1, EN2)
The MAX5098A dual converter provides separate
enable inputs, EN1 and EN2, to individually control
or sequence the output voltages. These active-high
enable inputs are TTL compatible. Driving EN_ high
initiates soft-start of the converter, and PGOOD_ goes
logic-high when the converter output voltage reaches the
VTPGOOD_ threshold. Driving EN_ low initiates a soft-
stop of the converter, and immediately forces PGOOD_
low. Use EN1, EN2, and PGOOD1 for sequencing (see
Figure 2). Connect PGOOD1 to EN2 to make sure con-
verter 1’s output is within regulation before converter 2
starts. Add an RC network from VL to EN1 and EN2 to
delay the individual converter. Sequencing reduces input
inrush current and possible chattering. Connect EN_ to
VL for always-on operation.
PGOOD_
Converter 1 and converter 2 include a power-good flag,
PGOOD1 and PGOOD2, respectively. Since PGOOD_ is
an open-drain output and can sink 3mA while providing
the TTL logic-low signal, pull PGOOD_ to a logic voltage
to provide a logic-level output. PGOOD1 goes low when
converter 1’s feedback FB1 drops to 92.5% (VTPGOOD_)
of its nominal set point. The same is true for converter 2.
Connect PGOOD_ to SGND or leave unconnected if not
used.
Current Limit
The internal MOSFET switch current of each converter is
monitored during its on-time. When the peak switch cur-
rent crosses the current-limit threshold of 3.45A (typ) and
2.1A (typ) for converter 1 and converter 2, respectively,
the on-cycle is terminated immediately and the inductor
is allowed to discharge. The MOSFET is turned on at the
next clock pulse, initiating a new switching cycle.
In deep overload or short-circuit conditions when the
VFB_ voltage drops below 0.2V, the switching frequency
is reduced to 1/4 x fSW to provide sufficient time for the
inductor to discharge. During overload conditions, if the
voltage across the inductor is not high enough to allow
for the inductor current to properly discharge, current run-
away may occur. Current runaway can destroy the device
in spite of internal thermal-overload protection. Reducing
the switching frequency during overload conditions allows
more time for inductor discharge and prevents current
runaway.
www.maximintegrated.com Maxim Integrated
│
15
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Figure 1. Synchronized Controllers
SYNCSYNC
SLAVEMASTER
V+
OUTPUT4 OUTPUT3
DRAIN2
SOURCE2
DRAIN1
SOURCE1
CKO
CLKIN
V+
OUTPUT2 OUTPUT1
CIN
VIN
DRAIN2
SOURCE2
DRAIN1
SOURCE1
SYNC
SOURCE1
(MASTER)
CKO
(MASTER)
SOURCE2
(MASTER)
SOURCE1
(SLAVE)
SOURCE2
(SLAVE)
CKO
(SLAVE)
CIN (RIPPLE)
SYNCPHASE
CKOPHASE
DUTY CYCLE = 50%
www.maximintegrated.com Maxim Integrated
│
16
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Output Overvoltage Protection
The MAX5098A outputs are protected from output voltage
overshoots due to input transients and shorting the output
to a high voltage. When the output voltage rises above
the overvoltage threshold, 110% (typ) nominal FB_, the
overvoltage condition is triggered. When the overvoltage
condition is triggered on either channel, both convert-
ers are immediately turned off, 20Ω pulldown switches
from SOURCE_ to PGND_ are turned on to help the
output-voltage discharge, and the gate of the load-dump
protection external MOSFET is pulled low. The device
restarts as soon as both converter outputs discharge,
bringing both FB_ input voltages below 12.5V of their
nominal set points.
Thermal-Overload Protection
During continuous short circuit or overload at the output,
the power dissipation in the IC can exceed its limit. The
MAX5098A provides thermal shutdown protection with
temperature hysteresis. Internal thermal shutdown is pro-
vided to avoid irreversible damage to the device. When
the die temperature exceeds +165°C (typ), an on-chip
thermal sensor shuts down the device, forcing the internal
switches to turn off, allowing the IC to cool. The thermal
sensor turns the part on again with soft-start after the
junction temperature cools by +20°C. During thermal
shutdown, both regulators shut down, PGOOD_ goes
low, and soft-start resets. The internal 20V zener clamp
from IN_HIGH to SGND is not turned off during thermal
shutdown because clamping action must be always active.
Figure 2. Power-Supply Sequencing Configurations
FB1FB2
EN1EN2 VL
R1R2
C1C2
VL
VLV+
MAX5098A
OUTPUT2 OUTPUT1
DRAIN2
SOURCE2
DRAIN1
SOURCE1
VIN
VL
FB1FB2
EN1EN2
SEQUENCING—OUTPUT 2 DELAYED WITH RESPECT TO OUTPUT 1. R1/C1 AND R2/C2 ARE SIZED FOR REQUIRED SEQUENCING.
VL
VL
VLV+
MAX5098A
OUTPUT2 OUTPUT1
DRAIN2
SOURCE2
DRAIN1
SOURCE1
PGOOD1
VIN
VL
www.maximintegrated.com Maxim Integrated
│
17
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Applications Information
Setting the Switching Frequency
The controller generates the clock signal by dividing
down the internal oscillator fOSC or the SYNC input sig-
nal when driven by an external oscillator. The switching
frequency equals half the internal oscillator frequency
(fSW = fOSC/2). The internal oscillator frequency is set by
a resistor (ROSC) connected from OSC to SGND. To find
ROSC for each converter switching frequency fSW, use
the formulas:
( ) ( )
( )
( ) ( )
( )
OSC SW
0.920
SW
OSC SW
0.973
SW
10.721
R k f 1.25MHz
f MHz
12.184
R k f 1.25MHz
f MHz
Ω= ≥
Ω= <
A rising clock edge on SYNC is interpreted as a syn-
chronization input. If the SYNC signal is lost, the internal
oscillator takes control of the switching rate, returning
the switching frequency to that set by ROSC. When an
external synchronization signal is used, ROSC must be
selected such that fSW = 1/2 fSYNC. When fSYNC clock
signal is applied, fCKO equals fSYNC waveform, phase
shifted by 180°. If the MAX5098A is running without exter-
nal synchronization, fCKO equals the internal oscillator
frequency fOSC.
Buck Converter
Effective Input Voltage Range
Although the MAX5098A converter can operate from input
supplies ranging from 5.2V to 19V, the input voltage range
can be effectively limited by the MAX5098A duty-cycle
limitations for a given output voltage. The maximum input
voltage is limited by the minimum on-time (tON(MIN)):
OUT
IN(MAX) ON(MIN) SW
V
V
tf
≤×
where tON(MIN) is 100ns. The minimum input voltage is
limited by the maximum duty cycle (DMAX = 0):
OUT DROP1
IN(MIN) DROP2 DROP1
MAX
VV
V VV
D−
+
= +
where VDROP1 is the total parasitic voltage drops in the
inductor discharge path, which includes the forward
voltage drop (VD) of the rectifier, the series resistance
of the inductor, and the PCB resistance. VDROP2 is the
total resistance in the charging path that includes the
on-resistance of the high-side switch, the series resis-
tance of the inductor, and the PCB resistance.
Setting the Output Voltage
For 0.8V or greater output voltages, connect a voltage-di-
vider from OUT_ to FB_ to SGND (Figure 3). Select
RB (FB_ to SGND resistor) to between 1kΩ and 20kΩ.
Calculate RA (OUT_ to FB_ resistor) with the following
equation:
OUT_
AB FB_
V
RR 1
V−
=
where VFB_ = 0.8V (see the Electrical Characteristics
table) and VOUT_ can range from VFB_ to 28V (boost
operation).
For output voltages below 0.8V, set the MAX5098A output
voltage by connecting a voltage-divider from OUT_ to
FB_ to BYPASS (Figure 3). Select RC (FB_ to BYPASS
resistor) in the 50kΩ range. Calculate RA with the follow-
ing equation:
FB_ OUT_
AC
BYPASS FB_
VV
RR
VV
−
−
=
where VFB_ = 0.8V, VBYPASS = 2V (see the Electrical
Characteristics table), and VOUT_ can range from 0V to
VFB_.
Figure 3. Adjustable Output Voltage
RA
VOUT_
VOUT_
SOURCE_
FB_
VOUT_ 0.8V
RB
MAX5098A
RC
FB_
SOURCE_
BYPASS
VOUT_ < 0.8V
RA
MAX5098A
www.maximintegrated.com Maxim Integrated
│
18
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Inductor Selection
Three key inductor parameters must be specified for
operation with the MAX5098A: inductance value (L),
peak inductor current (IL), and inductor saturation current
(ISAT). The minimum required inductance is a function
of operating frequency, input-to-output voltage differen-
tial and the peak-to-peak inductor current (∆IL). A good
compromise is to choose ∆IL equal to 30% of the full load
current. To calculate the inductance, use the following
equation:
( )
OUT IN OUT
IN SW L
V VV
LVf I
−
=× ×∆
where VIN and VOUT are typical values (so that effi-
ciency is optimum for typical conditions). The switching
frequency is set by ROSC (see the Setting the Switching
Frequency section). The peak-to-peak inductor current,
which reflects the peak-to-peak output ripple, is worse
at the maximum input voltage. See the Output Capacitor
section to verify that the worst-case output ripple is
acceptable. The inductor saturation current is also import-
ant to avoid runaway current during output overload and
continuous short circuit. Select the ISAT to be higher than
the maximum peak current limits of 4.3A and 2.6A for
converter 1 and converter 2.
Input Capacitor
The discontinuous input current waveform of the buck
converter causes large ripple currents at the input. The
switching frequency, peak inductor current, and the
allowable peak-to-peak voltage ripple dictate the input
capacitance requirement. Note that the two converters of
the MAX5098A run 180° out-of-phase, thereby effectively
doubling the switching frequency at the input.
The input ripple waveform would be unsymmetrical
due to the difference in load current and duty cycle
between converter 1 and converter 2. The worst-case
misatch is when one converter is at full load while the
other converter is at no load or in shutdown. The input
ripple is comprised of ∆VQ (caused by the capacitor dis-
charge) and ∆VESR (caused by the ESR of the capacitor).
Use ceramic capacitors with high ripple-current capability
at the input, connected between DRAIN_ and PGND_.
Assume the contribution from the ESR and capacitor
discharge equal to 50%. Calculate the input capacitance
and ESR required for a specified ripple using the following
equations:
ESR
IN L
OUT
V
ESR I
I
2
∆
=∆
+
where
( )
IN OUT OUT
L
IN SW
VV V
IVf L
−×
∆= ××
and
( )
OUT
IN
Q SW
I D1 D
CVf
−×
=∆×
where
OUT
IN
V
DV
=
where IOUT is the maximum output current from either
converter 1 or converter 2, and D is the duty cycle for that
converter. The frequency of each individual converter is
fSW. For example, at VIN = 12V, VOUT = 3.3V at IOUT =
2A, and with L = 3.3µH, the ESR and input capacitance
are calculated for a peak-to-peak input ripple of 100mV
or less, yielding an ESR and capacitance value of 20mΩ
and 6.8µF for 1.25MHz frequency. At low input voltages,
also add one electrolytic bulk capacitor of at least 100µF
on the converters’ input voltage rail. This capacitor acts as
an energy reservoir to avoid possible undershoot below
the undervoltage lockout threshold during power-on and
transient loading.
Output Capacitor
The allowable output ripple voltage and the maximum
deviation of the output voltage during step load currents
determines the output capacitance and its ESR. The
output ripple is comprised of ∆VQ (caused by the capac-
itor discharge) and ∆VESR (caused by the ESR of the
capacitor). Use low-ESR ceramic or aluminum electrolytic
capacitors at the output. For aluminum electrolytic capac-
itors, the entire output ripple is contributed by ∆VESR. Use
the ESROUT equation to calculate the ESR requirement
and choose the capacitor accordingly. If using ceramic
capacitors, assume the contribution to the output ripple
voltage from the ESR and the capacitor discharge are
equal. Calculate the output capacitance and ESR required
for a specified ripple using the following equations:
ESR
OUT L
L
OUT
Q SW
V
ESR I
I
C8V f
∆
=∆
∆
=×∆ ×
www.maximintegrated.com Maxim Integrated
│
19
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
where
O_RIPPLE ESR Q
V VV∆ ≅∆ +∆
∆IL is the peak-to-peak inductor current as calculated
above and fSW is the individual converter’s switching
frequency.
The allowable deviation of the output voltage during fast
transient loads also determines the output capacitance
and its ESR. The output capacitor supplies the step load
current until the controller responds with a greater duty
cycle. The response time (tRESPONSE) depends on the
closed-loop bandwidth of the converter. The high switch-
ing frequency of the MAX5098A allows for higher closed-
loop bandwidth, reducing tRESPONSE and the output
capacitance requirement. The resistive drop across the
output capacitor ESR and the capacitor discharge causes
a voltage droop during a step load. Use a combination of
low-ESR tantalum or polymer and ceramic capacitors for
better transient load and ripple/noise performance. Keep
the maximum output voltage deviation within the tolerable
limits of the electronics being powered. When using a
ceramic capacitor, assume 80% and 20% contribution
from the output capacitance discharge and the ESR drop,
respectively. Use the following equations to calculate the
required ESR and capacitance value:
ESR
OUT STEP
STEP RESPONSE
OUT
Q
V
ESR I
It
CV
∆
=
×
=∆
where ISTEP is the load step and tRESPONSE is the
response time of the controller. Controller response time
depends on the control-loop bandwidth.
Boost Converter
The MAX5098A can be configured for step-up conversion
since the internal MOSFET can be used as a low-side
switch. Use the following equations to calculate the val-
ues for the inductor (LMIN), input capacitor (CIN), and
output capacitor (COUT) when using the converter in
boost operation.
Inductor
Choose the minimum inductor value so the converter
remains in continuous mode operation at minimum output
curt (IOMIN)
2
IN
MIN SW O OMIN
VD
L2f V I
×
=× ××
where
O D IN
O D DS
V VV
DV VV
−
−
+
=+
The VD is the forward voltage drop of the external
Schottky diode, D is the duty cycle, and VDS is the volt-
age drop across the internal MOSFET switch. Select the
inductor with low DC resistance and with a saturation
current (ISAT) rating higher than the peak switch current
limit of 4.3A (ICL1) and 2.6A (ICL2) of converter 1 and
converter 2, respectively.
Input Capacitor
The input current for the boost converter is continuous
and the RMS ripple current at the input is low. Calculate
the capacitor value and ESR of the input capacitor using
the following equations.
L
IN SW Q
ESR
L
I
C8f V
V
ESR I
∆
=× ×∆
∆
=∆
where
( )
IN DS
L
SW
VV D
ILf
−×
∆= ×
where VDS is the voltage drop across the internal
MOSFET switch. ∆IL is the peak-to-peak inductor ripple
current as calculated above. ∆VQ is the portion of input
ripple due to the capacitor discharge and ∆VESR is the
contribution due to ESR of the capacitor.
Output Capacitor
For the boost converter, the output capacitor supplies the
load current when the main switch is ON. The required
output capacitance is high, especially at higher duty
cycles. Also, the output capacitor ESR needs to be low
enough to minimize the voltage drop due to the ESR while
supporting the load current. Use the following equation to
calculate the output capacitor for a specified output ripple
tolerance.
ESR
PK
O MAX
OUT Q SW
V
ESR I
ID
CVf
∆
=
×
=∆×
where IPK is the peak inductor current as defined in the
Power Dissipation section for the boost converter, IO is
the load current, ∆VQ is the portion of the ripple due to
www.maximintegrated.com Maxim Integrated
│
20
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
the capacitor discharge, and ∆VESR is the contribution
due to the ESR of the capacitor. DMAX is the maximum
duty cycle at minimum input voltage.
Power Dissipation
The MAX5098A includes two internal power MOSFET
switches. The DC loss is a function of the RMS current in
the switch while the switching loss is a function of switching
frequency and instantaneous switch voltage and current.
Use the following equations to calculate the RMS cur-
rent, DC loss, and switching loss of each converter. The
MAX5098A is available in a thermally enhanced package
and can dissipate up to 2.7W at +70°C ambient tempera-
ture. The total power dissipation in the package must be
limited so that the operating junction temperature does not
exceed its absolute maximum rating of +150°C at maxi-
mum ambient temperature.
For the buck converter
( )
()
22 MAX
RMS DC PK DC PK
2
DC RMS DS(ON)MAX
D
I I I II 3
PI R
= + +× ×
= ×
where
( )
L
DC O
L
PK O
IN O R F SW
SW
I
II2
I
II2
VI tt f
P
4
−∆
=
∆
= +
×× + ×
=
See the Electrical Characteristics table for the RON(MAX)
maximum value.
For the boost converter:
( )
()
( )
22 MAX
RMS DC PK DC PK
OO
IN IN
IN DS
LSW
L
DC IN
L
PK IN
2
DC RMS DS(ON)(MAX)
D
I I I II 3
VI
IV
VV D
ILf
I
II2
I
II 2
PI R
−
−
= + +× ×
×
=×h
×
∆= ×
∆
=
∆
= +
= ×
where VDS is the drop across the internal MOSFET and
h is the efficiency. See the Electrical Characteristics table
for the RON(MAX) value.
( )
O IN R F SW
SW
VI t t f
P
4
×× + ×
=
where tR and tF are rise and fall times of the internal
MOSFET. tF can be measured in the actual application.
The supply current in the MAX5098A is dependent on
the switching frequency. See the Typical Operating
Characteristics to find the supply current of the
MAX5098A at a given operating frequency. The power
dissipation (PS) in the device due to supply current
(ISUPPLY) is calculated using following equation.
PS = VINMAX x ISUPPLY
The total power dissipation PT in the device is:
PT = PDC1 + PDC2 + PSW1 + PSW2 + PS
where PDC1 and PDC2 are DC losses in converter 1 and
converter 2, respectively. PSW1 and PSW2 are switching
losses in converter 1 and converter 2, respectively.
Calculate the temperature rise of the die using the follow-
ing equation:
TJ = TC x (PT x θJC)
where θJC is the junction-to-case thermal impedance
of the package equal to +1.7°C/W. Solder the exposed
pad of the package to a large copper area to minimize
the case-to-ambient thermal impedance. Measure the
temperature of the copper area near the device at
a worst-case condition of power dissipation and use
+1.7°C/W as θJC thermal impedance.
Compensation
The MAX5098A provides an internal transconductance
amplifier with its inverting input and its output available
for external frequency compensation. The flexibility of
external compensation for each converter offers wide
selection of output filtering components, especially the
output capacitor. For cost-sensitive applications, use
aluminum electrolytic capacitors; for component size-sen-
sitive applications, use low-ESR tantalum, polymer, or
ceramic capacitors at the output. The high switching
frequency of MAX5098A allows use of ceramic capacitors
at the output.
Choose all the passive power components that meet
the output ripple, component size, and component cost
requirements. Choose the small-signal components for
the error amplifier to achieve the desired closed-loop
www.maximintegrated.com Maxim Integrated
│
21
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
bandwidth and phase margin. Use a simple pole-zero pair
(Type II) compensation if the output capacitor ESR zero
frequency is below the unity-gain crossover frequency
(fC). Type III compensation is necessary when the ESR
zero frequency is higher than fC or when compensating
for a continuous mode boost converter that has a right-
half-plane zero.
Use procedure 1 to calculate the compensation network
components when fZERO,ESR < fC.
Buck Converter Compensation
Procedure 1 (See Figure 4)
1) Calculate the fZERO,ESR and LC double-pole fre-
quencies:
ZERO,ESR OUT
LC
OUT OUT
1
f2 ESR C
1
f2L C
=π× ×
=π×
2) Select the unity-gain crossover frequency:
SW
C
f
f
20
≤
If the fZERO,ESR is lower than fC and close to fLC, use
a Type II compensation network where RFCF provides a
midband zero fMID,ZERO, and RFCCF provides a high-fre-
quency pole.
3) Calculate modulator gain GM at the crossover frequen-
cy.
( )
IN
MOSC C OUT OUT
VESR 0.8
GV ESR 2 f L V
=××
+ π× ×
where VOSC is a peak-to-peak ramp amplitude equal to
1V.
The transconductance error amplifier gain is:
GE/A = gM x RF
The total loop gain at fC should be equal to 1:
GM x GE/A = 1
or
( )
OSC C OUT OUT
FIN M
V ESR 2 f L V
R0.8 V g ESR
+ π× × ×
=× ××
4) Place a zero at or below the LC double pole:
F
F LC
1
C2R f
=π× ×
5) Place a high-frequency pole at fP = 0.5 x fSW.
( )
F
CF SW F F
C
C2 0.5f R C 1
−
=π× × ×
Procedure 2 (See Figure 5)
If the output capacitor used is a low-ESR ceramic type,
the ESR frequency is usually far away from the target-
ed unity crossover frequency (fC). In this case, Type III
compensation is recommended. Type III compensation
provides two-pole zero pairs. The locations of the zero
and poles should be such that the phase margin peaks
around fC. It is also important to place the two zeros at
or below the double pole to avoid the conditional stability
issue.
1) Select a crossover frequency:
SW
C
f
f
20
≤
2) Calculate the LC double-pole frequency, fLC:
LC
OUT OUT
1
f2L C
=π× ×
Figure 4. Type II Compensation Network
R1
FB_
RF
COMP_
VOUT
VREF
CCF
CF
R2
-
+
gM
www.maximintegrated.com Maxim Integrated
│
22
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Z1 LC
FF
1
f at 0.75 f .
2R C
= ×
π× ×
3) Place a zero
where
F
LC F
1
C2 0.75 f R
=π× × ×
and RF ≥ 10kΩ.
4) Calculate CI for a target unity crossover frequency, fC.
C OUT OUT OSC
I
IN F
2f L C V
CVR
π× × × ×
=×
5) Place a pole P1 ZERO,ESR
II
1
f at f
2 RC
=π× ×
or 5 x fC,
whichever
is lower,
I
P1 I
1
R
2f C
=π× ×
6) Place a second zero, fZ2, at 0.2 x fC or at fLC,
whichever is lower.
I
Z2 I
1
R1 R
2f C
−=π× ×
7) Place a second pole at 1/2 the switching frequency.
( )
F
CF SW F F
C
C2 0.5 f R C 1
−
=π× × × ×
Boost Converter Compensation
The boost converter compensation gets complicated due
to the presence of a right-half-plane zero fZERO,RHP. The
right-half-plane zero causes a drop in phase while adding
positive (+1) slope to the gain curve. It is important to
drop the gain significantly below unity before the RHP
frequency. Use the following procedure to calculate the
compensation components:
1) Calculate the LC double-pole frequency, fLC, and the
right-half-plane-zero frequency.
LC
OUT OUT
1D
f2L C
−
=π× ×
( )
( )
2
MIN
ZERO,RHP
OUT
1D R
f2L
−
=π×
where
( )
IN
OUT
OUT
MIN OUT(MAX)
V
D1
V
V
RI
−=
=
Figure 6. Boost Application
Figure 5. Type III Compensation Network
PGND_
DRAIN_
MAX5098A
VL
VDRV
V+
VOUT_
BST_/VDD_
COUT
SGND
PGND_
DRAIN_
SOURCE_
SOURCE_
FB_
R1 RF
COMP_
VOUT
VREF
R2
RI
CI
CF
CCF
-
+
gM
FB_
www.maximintegrated.com Maxim Integrated
│
23
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Target the unity-gain crossover frequency for:
ZERO,RHP
C
f
f
5
≤
Place a zero Z1 LC
FF
1
f at 0.75 f .
2R C
= ×
π× ×
where RF ≥ 10kΩ.
3) Calculate CI for a target crossover frequency, fC:
( )
22
OSC C OUT OUT
IC F IN
V 1D L C
CRV
−
+ω
=ω
where ωC = 2π fC:
4) Place a pole P1 ZERO,RHP
II
1
f at f .
2 RC
=π× ×
IZERO,RHP I
1
R2f C
=π× ×
5) Place the second zero Z2 LC
I
1
f at f .
2 R1 C
=π× ×
where
I
LC I
1
R1 R
2f C
−=π× ×
6) Place the second pole P2
F CF
1
f at 1 / 2
2R C
=π× ×
the switching frequency.
( )
F
CF SW F F
C
C
2 0.5 f R C 1
−
=π× × × ×
Load-Dump Protection MOSFET
Select the external MOSFET with an adequate voltage
rating, VDSS, to withstand the maximum expected load-
dump input voltage. The on-resistance of the MOSFET,
RDS(ON), should be low enough to maintain a minimal
voltage drop at full load, limiting the power dissipation of
the MOSFET.
During regular operation, the power dissipated by the
MOSFET is:
PNORMAL = ILOAD2 x RDS(ON)
where ILOAD is equal to the sum of both converters’ input
currents.
The MOSFET operates in a saturation region during load
dump, with both high voltage and current applied. Choose
a suitable power MOSFET that can safely operate in
the saturation region. Verify its capability to support the
downstream DC-DC converters input current during the
load-dump event by checking its safe operating area
(SOA) characteristics. Since the transient peak power
dissipation on the MOSFET can be very high during the
load-dump event, also refer to the thermal impedance
graph given in the data sheet of the power MOSFET to
make sure its transient power dissipation is kept within the
recommended limits.
Improving Noise Immunity
In applications where the MAX5098A is subject to noisy
environments, adjust the controller’s compensation
to improve the system’s noise immunity. In particular,
high-frequency noise coupled into the feedback loop
causes jittery duty cycles. One solution is to lower the
crossover frequency (see the Compensation section).
www.maximintegrated.com Maxim Integrated
│
24
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching
losses and clean, stable operation. This is especially true
for dual converters where one channel can affect the
other. Refer to the MAX5099 Evaluation Kit data sheet
for a specific layout example. Use a multilayer board
whenever possible for better noise immunity. Follow these
guidelines for good PCB layout:
1) For SGND, use a large copper plane under the IC and
solder it to the exposed paddle. To effectively use this
copper area as a heat exchanger between the PCB
and ambient, expose this copper area on the top and
bottom side of the PCB. Do not make a direct con-
nection from the exposed pad copper plane to SGND
underneath the IC.
2) Isolate the power components and high-current path
from the sensitive analog circuitry.
3) Keep the high-current paths short, especially at the
ground terminals. This practice is essential for stable,
jitter-free operation.
4) Connect SGND and PGND_ together at a single point.
Do not connect them together anywhere else (refer to
the MAX5099 Evaluation Kit data sheet for more infor-
mation).
5) Keep the power traces and load connections short.
This practice is essential for high efficiency. Use thick
copper PCBs (2oz vs. 1oz) to enhance full-load effi-
ciency.
6) Ensure that the feedback connection to COUT is short
and direct.
7) Route high-speed switching nodes (BST_/VDD_,
SOURCE_) away from the sensitive analog areas
(BYPASS, COMP_, and FB_). Use the internal PCB
layer for SGND as an EMI shield to keep radiated
noise away from the IC, feedback dividers, and analog
bypass capacitors.
Layout Procedure
1) Place the power components first, with ground ter-
minals adjacent (inductor, CIN_, and COUT_). Make
all these connections on the top layer with wide, cop-
per-filled areas (2oz copper recommended).
2) Group the gate-drive components (bootstrap diodes
and capacitors, and VL bypass capacitor) together
near the controller IC.
3) Make the DC-DC controller ground connections as
follows:
a) Create a small, signal ground plane underneath the
IC.
b) Connect this plane to SGND and use this plane for
the ground connection for the reference (BYPASS),
enable, compensation components, feedback
dividers, and OSC resistor.
c) Connect SGND and PGND_ together (this is the
only connection between SGND and PGND_).
Refer to the MAX5099 Evaluation Kit data sheet for
more information.
www.maximintegrated.com Maxim Integrated
│
25
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Figure 7. 4.5V to 5.5V Operation
BST2/VDD2
SOURCE2
SOURCE2
PGND1
FB2
COMP2
PGOOD2
EN2
SYNC
31
1
32
29
6
7
4
5
9
C6
D1
26
25
24
28
D2
C7
L1
C20
C9 R9
C8
R6
R22
R7
R8
R12 C11
C12 C13
19
18
21
VOUT1
PGND
SGND 20
17
CLOCK OUT
VL
VIN
VDRV
BST1/VDD1
SOURCE1
SOURCE1
CKO
FB1
COMP1
PGOOD1
EN1
FSEL_1
IN_HIGH
ON/OFF
GATE
V+
DRAIN1
DRAIN1
DRAIN2
DRAIN2
OSC
BYPASS
SGND
VDRV
VL
12 22 23 2 3
11 10 13
C1
C19 C4 C15
816 15 1427
PGND2
30
VIN = 4.5V
TO 5.5V
MAX5098A
VIN
PGND
C14
D4
D5 C5
L2
C21
C17
R18 C16
R15
R23
R16
R17
VOUT2
PGND
SGND
VDRV
www.maximintegrated.com Maxim Integrated
│
26
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
BST2/VDD2
SOURCE2
SOURCE2
PGND1
FB2
COMP2
PGOOD2
EN2
SYNC
31
1
32
29
6
7
4
5
9
C6
0.1F
D1
26
25
24
28
D2
C7
22F
C2
4.7F
35V
L1
4.7H
C20
33pF
C9
2700pF R9
12.7Ω
C8
270pF
R6
52.3kΩ
1%
R22
10kΩ
1% R7
10kΩ
1%
R8
976Ω
1%
R12
6.49Ω
C11
0.22F
C12
2.2F
C13
4.7F
19
18
21
VOUT1
PGND
SGND 20
17
CLOCK OUT
VL
VDRV
BST1/VDD1
SOURCE1
SOURCE1
CKO
FB1
COMP1
PGOOD1
EN1
FSEL_1
IN_HIGH
ON/OFF
GATE
V+
DRAIN1
DRAIN1
DRAIN2
DRAIN2
OSC
BYPASS
SGND
VDRV
V
L
N1
R1
3.9kΩ
12 22 23 2 3
11 10 13
C1
22F
100V
C3
150F
25V
C19
1F
25V
C4
10F
25V
C15
10F
25V
816
VDRV
15 1427
PGND2
30
VIN = 5.2V
TO 19V
VOUT1 =
5V AT 2A
R21
1Ω
MAX5098A
VIN
PGND
C14
0.1F
D4
D5
C5
22F
L2
4.7H
C21
56pF
C17
2700pF
R18
7.15ΩC16
270pF
R15
37.4kΩ
1%
R23
10kΩ
1%
R16
12.1kΩ
1%
R17
976Ω
1%
VOUT2
PGND
SGND
VDRV
VOUT2 = 3.3V
AT 1A
www.maximintegrated.com Maxim Integrated
│
27
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Typical Application Circuit
MAX5098A
TQFN
(5mm x 5mm)
TOP VIEW
29
30
+
28
27
*EP
*EP = EXPOSED PAD.
12
11
13
DRAIN2
PGOOD2
EN2
FB2
COMP2
14
SOURCE2
DRAIN1
PGOOD1
EN1
SOURCE1
FB1
COMP1
1 2
CKO
4 5 6 7
2324 22 20 19 18
PGND1
PGND2
VL
V+
IN_HIGH
ON/OFF
DRAIN2 DRAIN1
3
21
31 10
BST2/VDD2 GATE
32 9
SOURCE2 SYNC
VDRV
26 15 SGND
BST1/VDD1
25 16 BYPASS
OSC FSEL_1
8
17
SOURCE1
Pin Conguration Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
32 TQFN-EP T3255+4
21-0140 90-0012
www.maximintegrated.com Maxim Integrated
│
28
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 5/08 Initial release —
1 10/14 Removed “Automotive” from the title; changed automotive references to industrial in the
General Description and Applications; removed the Load Dump Protection section 1, 14
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
MAX5098A Dual 2.2MHz Buck or Boost Converter
with 80V Load-Dump Protection
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2014 Maxim Integrated Products, Inc.
│
29
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
