_______________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX8969
Step-Up Converter
for Handheld Applications
19-6038; Rev 1; 5/12
Typical Operating Circuit
General Description
The MAX8969 is a simple 1A step-up converter in a small
package that can be used in any single-cell Li-ion appli-
cation. This IC provides protection features such as input
undervoltage lockout, short circuit, and overtemperature
shutdown.
The IC transitions to skip mode seamlessly under light-
load conditions to improve efficiency. Under these
conditions, switching occurs only as needed, reducing
switching frequency and supply current to maintain high
efficiency.
When the input voltage is sufficient to drive the load, the
IC can be operated in track mode or automatic track
mode (ATM). In track mode, the p-channel MOSFET acts
as a current-limited load switch and quiescent current is
as low as 30µA under a no-load condition. In ATM mode,
the p-channel MOSFET acts as a current-limited load
switch and quiescent current is as low as 60µA under a
no-load condition. In ATM mode, the internal boost cir-
cuitry is enabled, allowing for fast transitions into boost
mode.
The IC is available in a small, 1.25mm x 1.25mm, 9-bump
WLP (0.4mm pitch) package.
Applications
Cell Phones
Smartphones
Mobile Internet Devices
GPS, PND
eBooks
Features
S Compact Layout
Small, 1.25mm x 1.25mm WLP Package
3MHz PWM Switching Frequency
Small External Components
S Safe and Efficient Step-Up Mode
Up to 1A Output Current
2.5V to 5.5V Input Voltage Range
3.3V to 5V Ouput Voltage Range
Over 90% Efficiency with Internal Synchronous
Rectifier
Low 45µA No-Load Quiescent Current
Soft-Start Controls Inrush Current
True Shutdown™
Low 1µA Shutdown Current
S Track Mode
1A Current Limited
130mI On-Resistance
Low 30µA No Load Quiescent Current
S Automatic Track Mode
130mI On-Resistance
Low 60µA No-Load Quiescent Current
Boost Circuitry Enabled for Fast Transition into
Boost
True Shutdown is a trademark of Maxim Integrated Products, Inc.
Note: The output voltage range is from 3.3V to 5V. Contact the
factory for output options and availability.
+Denotes a lead(Pb)-free/RoHS-compliant package.
Ordering Information
EVALUATION KIT
AVAILABLE
IN OUT_
LX_
GND_
CIN
4.7µF
L1
1µH
COUT
22µF
INPUT
2.5V TO 5.5V
OUTPUT
3.7V, 1A
EN
MAX8969
TREN
PART VOUT
(V) TEMP RANGE PIN-
PACKAGE
MAX8969EWL33+ 3.3 -40NC to +85NC9 WLP
MAX8969EWL35+ 3.5 -40NC to +85NC9 WLP
MAX8969EWL37+ 3.7 -40NC to +85NC9 WLP
MAX8969EWL42+ 4.25 -40NC to +85NC9 WLP
MAX8969EWL50+ 5.0 -40NC to +85NC9 WLP
2 ______________________________________________________________________________________
MAX8969
Step-Up Converter
for Handheld Applications
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.
IN, OUT_ to GND_ ................................................-0.3V to +6.0V
EN, TREN to GND_ ............ -0.3V to lower of (VIN + 0.3V) or 6V
Total LX_ Current ...........................................................3.2ARMS
OUT_ Short Circuit to GND_ .....................................Continuous
Continuous Power Dissipation (TA = +70NC)
WLP (derate 12mW/NC above +70NC).........................960mW
Operating Temperature Range .......................... -40NC to +85NC
Junction Temperature .....................................................+150NC
Storage Temperature Range ............................ -65NC to +150NC
Soldering Temperature (reflow) (Note 1) ........................+260NC
ELECTRICAL CHARACTERISTICS
(VIN = 2.6V, TA = -40NC to +85NC, unless otherwise noted. Typical values are TA = +25NC.) (Note 3)
ABSOLUTE MAXIMUM RATINGS
Note 1: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile that the
device can be exposed to during board level solder attach and rework. This limit permits only the use of the solder pro-
files recommended in the industry-standard specification JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection
reflow. Preheating is required. Hand or wave soldering is not allowed.
WLP
Junction-to-Ambient Thermal Resistance (BJA) ..........83NC/W
Junction-to-Case Thermal Resistance (BJC) ...............50NC/W
PACKAGE THERMAL CHARACTERISTICS (Note 2)
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Operating Input Voltage Range 2.5 5.5 V
Minimum Startup Voltage 2.3 V
Undervoltage Lockout Threshold (UVLO) VIN falling, 75mV hysteresis 2.1 2.2 2.3 V
Shutdown Supply Current VEN = VTREN = VOUT = 0V,
VIN = 4.8V
TA = +25NC0.8 5 FA
TA = +85NC1
Thermal Shutdown TA rising, 20NC hysteresis +165 NC
BOOST MODE
Peak Output Current VIN > 2.5V (Note 4) 1 A
Continuous Output Current VIN > 2.5V, pulse
load
VOUT = 3.3V 0.9
A
VOUT = 3.5V 0.8
VOUT = 3.7V 0.7
VOUT = 4.25V 0.7
VOUT = 4.7V 0.7
VOUT = 5.0V 0.7
Switching Frequency (Note 4) 3 MHz
Output Voltage Accuracy
No load, VOUT_TARGET = 3.3V 3.175 3.30 3.40
V
No load, VOUT_TARGET = 3.5V 3.40 3.50 3.60
No load, VOUT_TARGET = 3.7V 3.64 3.75 3.85
No load, VOUT_TARGET = 4.25V 4.10 4.25 4.35
No load, VOUT_TARGET = 5V 4.85 5.00 5.10
_______________________________________________________________________________________ 3
MAX8969
Step-Up Converter
for Handheld Applications
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 2.6V, TA = -40NC to +85NC, unless otherwise noted. Typical values are TA = +25NC.) (Note 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Steady-State Output Voltage
(Notes 5, 6)
2.5V < VIN < VATMRT, conditions emulating 0 <
IOUT < 1A, COUT = 22FF, L = 1FH,
VOUT_TARGET = 3.3V
3.00 3.45
V
2.5V < VIN < VATMRT, conditions emulating 0 <
IOUT < 1A, COUT = 22FF, L = 1FH,
VOUT_TARGET = 3.5V
3.15 3.65
2.5V < VIN < VATMRT, conditions emulating 0 <
IOUT < 1A, COUT = 22FF, L = 1FH,
VOUT_TARGET = 3.7V
3.35 3.85
2.5V < VIN < VATMRT, conditions emulating 0 <
IOUT < 600mA, COUT = 22FF, L = 1FH,
VOUT_TARGET = 4.25V
3.95 4.35
2.5V < VIN < VATMRT, conditions emulating 0 <
IOUT < 500mA, COUT = 22FF, L = 1FH,
VOUT_TARGET = 5V
4.50 5.10
LX_ Leakage Current VLX = 0V, 4.8V TA = +25NC0.1 5 FA
TA = +85NC0.2
Skip-Mode Supply Current EN = high, IOUT = 0A, 1FH inductor (TREN is
low, not switching) 45 FA
pMOS Turn-Off Current (Zero-Cross Current) 10 mA
LX_ nMOS Current Limit 2.6 3.2 A
Maximum Duty Cycle 83 %
Minimum Duty Cycle 0 %
pMOS On-Resistance
VOUT = 3.3V 120
mI
VOUT = 3.5V 115
VOUT = 3.7V 110
VOUT = 4.25V 100
VOUT = 5V 91
nMOS On-Resistance
VOUT = 3.3V 65
mI
VOUT = 3.5V 63
VOUT = 3.7V 60
VOUT = 4.25V 55
VOUT = 5V 51
Minimum Output Capacitance for Stable
Operation (Actual) 8FF
Maximum Output Capacitance (Actual) 0 < IOUT < 0.3A
during startup
VOUT = 3.3V 70
FF
VOUT = 3.5V 55
VOUT = 3.7V 45
VOUT = 4.25V 30
VOUT = 5V 20
4 ______________________________________________________________________________________
MAX8969
Step-Up Converter
for Handheld Applications
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 2.6V, TA = -40NC to +85NC, unless otherwise noted. Typical values are TA = +25NC.) (Note 3)
Note 3: Specifications are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by
design and characterization.
Note 4: Continuous operation with 1A at elevated ambient temperature and low voltage is not guaranteed. Under worst-case con-
ditions, die thermal protection cannot be activated after 100ms of 1A load application. See the continuous output current
parameter for a conservative estimate of current that can be maintained at TA = +85°C.
Note 5: Switching frequency decreases if input voltage is > 83% of the output voltage selected. This allows duty factor to drop to
values necessary to boost output voltage less than 25% without the use of pulse widths less than 60ns.
Note 6: Contact factory for other options.
Note 7: The output voltage regulation is a direct function of the peak current in the nMOS power switch. The inductor current (ILX)
described in the conditions of the steady-state output voltage specification corresponds to the peak inductor current.
Note 8: Once ATM threshold is reached boost switching stops in 1µs (typ), but the transition to ATM does not occur until VOUT has
fallen equal to VIN.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Voltage Ripple IOUT = 150mA, circuit of Figure 1 20 mVP-P
Soft-Start Interval IOUT = 10mA, see the Output Capacitor
Selection section Fs
TRACK MODE
pMOSFET On-Resistance IOUT = 500mA, VIN = 2.7V 130 mI
IOUT = 500mA, VIN = 3.2V 110
Track Current Limit VOUT = 3.6V 1 2 A
Track Mode Quiescent Current EN = low, TREN = high 30 FA
AUTOMATIC TRACK MODE (ATM)
ATM Supply Current VIN = 5.4V 65 FA
ATM VIN Rising Threshold (VATMRT)
VOUT_TARGET = 3.3V 3.15
V
VOUT_TARGET = 3.5V 3.35
VOUT_TARGET = 3.7V 3.55
VOUT_TARGET = 4.25V 4.04
VOUT_TARGET = 5V 4.74
ATM VIN Falling Threshold (VATMFT)
VOUT_TARGET = 3.3V 3.10
V
VOUT_TARGET = 3.5V 3.29
VOUT_TARGET = 3.7V 3.5
VOUT_TARGET = 4.25V 3.99
VOUT_TARGET = 5V 4.69
Boost to ATM Transition Time (Note 7) 1 Fs
ATM to Boost Transition Time 1 Fs
LOGIC CONTROL
EN, TREN Logic Input High Voltage 2.3V < VIN < 5.5V 1.05 V
EN, TREN Logic Input Low Voltage 2.3V < VIN < 5.5V 0.4 V
EN, TREN Leakage Current VEN = VTREN = 0V TA = +25NC-1 0.01 +1 FA
TA = +85NC0.1
_______________________________________________________________________________________ 5
MAX8969
Step-Up Converter
for Handheld Applications
Typical Operating Characteristics
(VIN = 3.6V, COUT = 22µF, X5R, 6.3V local and 10µF, X5R, 6.3V, 1µH inductor, circuit of Figure 1, TA = +25NC, unless otherwise noted.)
MAX8969 toc01
LOAD CURRENT (mA)
EFFICIENCY (%)
100101 1000
EFFICIENCY vs. OUTPUT CURRENT
(VOUT = 5V)
65
70
75
80
85
90
95
100 VIN = 4.3V
VIN = 3.6V
L = TOKO DFE252012 1µH
VIN = 2.5V
VIN = 3.1V
60
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX8969 toc04
INPUT VOLTAGE (V)
MAXIMUM OUTPUT CURRENT (mA)
5.04.54.03.53.0
1000
1500
2000
2500
3000
500
2.5 5.5
VOUT, 3.7V ≥ 3.35V
VOUT, 5V ≥ 4.5V
EFFICIENCY vs. OUTPUT CURRENT
(VOUT = 3.7V)
MAX8969 toc02
LOAD CURRENT (mA)
EFFICIENCY (%)
10010
82
84
86
88
90
92
94
96
98
100
80
1 1000
VIN = 2.5V
VIN = 3.1V
L = TOKO DFE252012 1µH
OUTPUT VOLTAGE (VOUT = 5V)
vs. OUTPUT CURRENT
MAX8969 toc05
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
800600400200
4.60
4.65
4.70
4.75
4.80
4.85
4.90
4.95
5.00
5.05
4.55
0 1000
VIN = 2.5V
VIN = 3.2V
VIN = 3.6V VIN = 4.3V
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX8969 toc03
INPUT VOLTAGE (V)
NO-LOAD SUPPLY CURRENT (uA)
5.04.53.0 3.5 4.0
VOUT = 3.7V
VOUT = 5V
10
20
30
40
50
60
70
80
0
2.5 5.5
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
800600400200
3.4
3.6
3.8
4.0
4.2
4.4
3.2
0 1000
OUTPUT VOLTAGE (VOUT = 3.7V)
vs. OUTPUT CURRENT
MAX8969 toc06
VIN = 3.2V
VIN = 4.3V
VIN = 2.5V
VIN = 3.6V
OUTPUT VOLTAGE (VOUT = 5V)
vs. INPUT VOLTAGE
MAX8969 toc07
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.04.54.03.53.0
3.5
4.0
4.5
IOUT = 1000mA
IOUT = 10mA IOUT = 100mA IOUT = 600mA
AUTOMATIC
FREQUENCY
ADJUSTMENT
AUTOMATIC
TRACK MODE
TRANSITION
5.0
5.5
3.0
2.5 5.5
OUTPUT VOLTAGE (VOUT = 3.7V)
vs. INPUT VOLTAGE
MAX8969 toc08
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
4.03.53.0
3.0
3.5
4.0
4.5
5.0
2.5
2.5 4.5
IOUT = 600mA
IOUT = 100mA
IOUT = 10mA
IOUT = 1000mA
AUTOMATIC
FREQUENCY
ADJUSTMENT
AUTOMATIC
TRACK MODE
TRANSITION
6 ______________________________________________________________________________________
MAX8969
Step-Up Converter
for Handheld Applications
Typical Operating Characteristics (continued)
(VIN = 3.6V, COUT = 22µF, X5R, 6.3V local and 10µF, X5R, 6.3V, 1µH inductor, circuit of Figure 1, TA = +25NC, unless otherwise noted.)
3.7V LINE TRANSIENT
MAX8969 toc09
2.6V
AC-COUPLED
100mV/div
3V
VOUT
VIN
100µs/div
TREN = VIN, IOUT = 200mA
3.7V LOAD TRANSIENT (0mA-50mA-0mA)
MAX8969 toc11
AC-COUPLED
50mV/div
5V/div
50mA
0
0
IOUT
VOUT
VLX
200µs/div
VIN = 2.6V
3.7V LOAD TRANSIENT
(50mA-500mA-50mA)
MAX8969 toc13
AC-COUPLED
200mV/div
5V/div
500mA
50mA
0
IOUT
VOUT
VLX
20µs/div
VIN = 2.8V
5V LINE TRANSIENT
MAX8969 toc10
3.3V
AC-COUPLED
100mV/div
3.7V
VOUT
VIN
100µs/div
TREN = VIN, IOUT = 200mA
5V LOAD TRANSIENT (0mA-50mA-0mA)
MAX8969 toc12
AC-COUPLED
50mV/div
5V/div
50mA
0
0
IOUT
VOUT
VLX
200µs/div
VIN = 3.8V
5V LOAD TRANSIENT
(50mA-500mA-50mA)
MAX8969 toc14
AC-COUPLED
100mV/div
5V/div
500mA
50mA
0
IOUT
VOUT
VLX
20µs/div
VIN = 3.8V
_______________________________________________________________________________________ 7
MAX8969
Step-Up Converter
for Handheld Applications
Typical Operating Characteristics
(VIN = 3.6V, COUT = 22µF, X5R, 6.3V local and 10µF, X5R, 6.3V, 1µH inductor, circuit of Figure 1, TA = +25NC, unless otherwise noted.)
LIGHT-LOAD RIPPLE
MAX8969 toc15
AC-COUPLED
20mV/div
2V/div
0
VOUT
VLX
40µs/div
IOUT = 1mA, VIN = 3.6V
STARTUP (VOUT = 5V)
MAX8969 toc17
2V/div
2V/div
0
0
2V/div
0
VEN
VOUT
VLX
200µs/div
COUT, TYP = 32µF,
TREN = GND,
IOUT = 10mA,
VIN = 3.2V
HARD-SHORT (VOUT = 5V)
MAX8969 toc19
2V/div
2A/div
0
0
0
2V/div
2A/div
0
VOUT
VLX
IOUT
VIN = 3.2V, 0.1I LOAD
ILX
20µs/div
STARTUP (VOUT = 3.7V)
MAX8969 toc16
2V/div
2V/div
0
0
2V/div
0
VEN
VOUT
VLX
200µs/div
COUT, TYP = 32µF,
TREN = GND,
IOUT = 10mA,
VIN = 2.6V
HARD-SHORT (VOUT = 3.7V)
MAX8969 toc18
2V/div
2A/div
0
0
0
2V/div
2A/div
0
VOUT
VLX
IOUT
VIN = 3.2V, 0.1I LOAD
ILX
40µs/div
SHUTDOWN
MAX8969 toc20
2V/div
0
0
0
2V/div
2V/div
VOUT
VEN
VLX
10I LOAD, TREN = GND
2µs/div
8 ______________________________________________________________________________________
MAX8969
Step-Up Converter
for Handheld Applications
Pin Configuration
Pin Description
TOP VIEW
(BUMP SIDE DOWN)
WLP
(1.25mm × 1.25mm)
OUT1 OUT2 IN
LX1 LX2 EN
GND1 GND2 TREN
A
B
C
123
MAX8969
+
PIN NAME FUNCTION
A1 OUT1 Power Output. Bypass OUT_ to ground with a 22FF rated ceramic capacitor. For optimal
performance place the ceramic capacitor as close as possible to OUT_. OUT1 and OUT2
should be shorted together directly under the IC. In True Shutdown, the output voltage can fall
to 0V, but OUT_ has a diode with its cathode connected to IN. See Figure 3.
A2 OUT2
A3 IN Input Supply Voltage. Bypass IN to GND_ with a 4.7FF ceramic capacitor. A larger
capacitance may be required to reduce noise.
B1 LX1 Converter Switching Node. Connect a 1FH inductor from LX_ to IN. LX_ is high impedance in
shutdown. LX1 and LX2 should be shorted together directly under the IC.
B2 LX2
B3 EN
Enable Input. Drive EN logic-high to enable boost mode, regardless of the logic level of TREN.
Connect EN to ground or drive logic-low to allow TREN to select either True Shutdown or track
mode. See Table 1.
C1 GND1 Ground. Connect GND_ to a large ground plane. GND1 and GND2 should be shorted together
directly under the IC.
C2 GND2
C3 TREN Track Enable Input. Drive TREN logic-high to enable track mode. Connect TREN to ground or
drive logic-low to place the IC in True Shutdown. See Table 1.
_______________________________________________________________________________________ 9
MAX8969
Step-Up Converter
for Handheld Applications
Figure 1. Functional Diagram
Detailed Description
The MAX8969 is a step-up DC-DC switching converter
that utilizes a fixed-frequency PWM architecture with
True Shutdown. With an advanced voltage-positioning
control scheme and high 3MHz switching frequency, the
IC is inexpensive to implement and compact, using only
a few small easily obtained external components. Under
light-load conditions, the IC switches only when needed,
consuming only 45FA (typ) of quiescent current. The IC
is highly efficient with an internal switch and synchronous
rectifier. Shutdown typically reduces the quiescent current
to 1FA (typ). Low quiescent current and high efficiency
make this device ideal for powering portable equipment.
Internal soft-start limits inrush current to less than 720mA
(typ), while output voltage is less than input voltage. Once
output voltage approaches input voltage approaches
input voltage after a brief delay, output voltage is boosted
to its final value at a rate of approximately 25mV/µs.
During this period, as well as being limited by the volt-
age, ramp rate current is limited by the normal 2.6A boost
mode current limit.
In boost mode, the step-up converter boosts to
VOUT_TARGET from battery input voltages ranging from
2.5V to VOUT_TARGET. When the input voltage ranges
from 0.95 x VOUT_TARGET to 5.5V, the IC enters ATM and
the output voltage approximately follows the input volt-
age. During boost mode, the input current limit is set to
2.6A to guarantee delivery of the rated out current (e.g.,
1A output current when boosting from a 2.5V input supply
to a 3.7V output).
Control Scheme
The step-up converter uses a load/line control scheme.
The load/line control scheme allows the output voltage
to sag under load, but prevents overshoot when the
load is suddenly removed. The load/line control scheme
reduces the total range of voltages reached during
transients at the expense of DC output impedance.
REFERENCE
CURRENT
LIMIT
CONTROL
LOGIC
L1
1µH
GND_
TREN
0.95 x
VOUT_TARGET
EN
IN
OUT_
CIN
4.7µF
COUT
22µF
LX_
ATM
P1
N1
ATM
COMPARATOR
TRACK
ENABLE
IN
PWM
LOGIC
RAMP
GENERATOR
TRUE
SHUTDOWN
IN
MAX8969
10 _____________________________________________________________________________________
MAX8969
Step-Up Converter
for Handheld Applications
Figure 2. State Diagram
TRUE SHUTDOWN
N1 = OFF
P1 = OFF
IQ = 1µA (typ)
TRACK MODE*
N1 = OFF
P1 = CURRENT-
LIMITED SWITCH
IQ = 30µA (typ)
AUTOMATIC TRACK
MODE (ATM)*
N1 = OFF
P1 = CURRENT-
LIMITED SWITCH
IQ = 65µA (typ)
BOOST CIRCUITRY ENABLED
VIN
COMPARATOR
BOOST SOFT-START
N1 = SWITCHING
P1 = OFF
BOOST EXIT MODE
N1 = OFF
P1 = OFF
IC WAITS UNTIL
VOUT = VIN
BOOST MODE
N1 = SWITCHING
P1 = SWITCHING
VOUT = VOUT_TARGET
IQ = 45µA (SKIP MODE)
UVLO, EXCESSIVE
TEMPERATURE,
OR SHORT CIRCUIT
FROM ANY STATE
EN = 1, OR
TREN = 1
EN = 0,
TREN = 0
EN = 0,
TREN = 0
1
0
EN = 1,
VOUT > (VIN - 300mV)
VIN
COMPARATOR = 0
VIN
COMPARATOR = 1
SOFT-START
VOLTAGE RAMP
COMPLETE
OUTPUT
BELOW TARGET
[VOUT < (0.72 x
VOUT_TARGET)]
VOUT < VIN,
TREN = 0
VOUT < VIN,
TREN = 1
EN = 0
EN = 0
*EN TAKES PRIORITY OVER TREN. SEE TABLE 1.
______________________________________________________________________________________ 11
MAX8969
Step-Up Converter
for Handheld Applications
Figure 3. Modes of Operation
P1 BODY DIODE
OUT_
P1 = OFF
N1 = OFF
LX_
IN
TRUE SHUTDOWN:
P1 BODY DIODE
OUT_
P1 = CURRENT-
LIMITED SWITCH
N1 = OFF
LX_
IN
TRACK/ATM MODE:
P1 BODY DIODE
OUT_
P1 = OFF
N1 = OFF
LX_
IN
BOOST EXIT MODE:
P1 BODY DIODE
OUT_
P1 = OFF
N1 = SWITCHING
LX_
IN
BOOST SOFT-START:
P1 BODY DIODE
OUT_
P1 = SWITCHING
N1 = SWITCHING
LX_
IN
BOOST MODE:
12 _____________________________________________________________________________________
MAX8969
Step-Up Converter
for Handheld Applications
The IC is designed to operate with the input voltage
range straddling its output voltage set point. Two tech-
niques are used to accomplish this. The first technique is
to activate ATM if the input voltage exceeds 95% of the
output set point; see the Automatic Track Mode (ATM)
section. The second technique is automatic frequency
adjustment.
Automatic Track Mode (ATM)
ATM is entered when an internal comparator signals that
the input voltage has exceeded the ATM threshold. The
ATM threshold is 95% of the output voltage target. At this
point, the IC enters ATM, with the pMOS switch turned
on, regardless of the status of TREN. Note that EN must
be high to enable ATM mode. This behavior is summa-
rized in Table 1.
Automatic Frequency Adjustment
Automatic frequency adjustment is used to maintain
stability if the input voltage is above 80% and below
95% of the output set point. Frequency adjustment is
required because the n-channel has a minimum on-time
of approximately 60ns. At 3MHz, this would lead to the
p-channel having a maximum duty factor of 82%. With
an input voltage more than 82% of the output set point,
the p-channel’s duty factor must be increased by reduc-
ing operating frequency either through cycle skipping
or adjusting the clock’s frequency. The IC adjusts its
clock frequency rather than simply skipping cycles. This
adjustment is done in two steps. The first step occurs if
the input voltage exceeds approximately 83% of the out-
put voltage and reduces clock speed to approximately
1.6MHz. The second step occurs if the input voltage is
greater than output voltage less 460mV. If this condition
is met, clock frequency is reduced to approximately
1MHz. Frequency adjustment allows the converter to
operate at a known frequency under all conditions.
Fault Protection
In track, ATM, and boost modes, the IC has protection
against overload and overheating.
• In track and ATM, current is limited to prevent
excessive inrush current during soft-start and to
protect against overload conditions. If the die tem-
perature exceeds +165°C in track/ATM, the switch
turns off until the die temperature has cooled to
+145NC.
• In boost mode, during each 3MHz switching cycle,
if the inductor current exceeds 2.6A, the n-channel
MOSFET is shut off and the p-channel MOSFET is
switched on. The end result is that LX_ current is
regulated to 2.6A or less. A 2.6A inductor current
is a large enough current to guarantee a 1A output
load current under all intended operating conditions.
The IC can operate indefinitely while regulating the
inductor current to 2.6A or less.
However, if a short circuit or extremely heavy load is
applied to the output, the output voltage decreases since
the inductor current is limited to 2.6A.
If the output voltage decreases to less than 72% of the
regulation voltage target (i.e., 2.8V with VOUT_TARGET of
3.7V), a short circuit is assumed, and the IC returns to
the shutdown state. The IC then attempts to start up if the
output short is removed. Even if the output short persists
indefinitely, the IC thermal protection ensures that the die
is not damaged.
True Shutdown
During operation in boost mode, the p-channel MOSFET
prevents current from flowing from OUT_ to LX_. In all
other modes of operation, it is desirable to block current
flowing from LX_ to OUT_. True Shutdown prevents current
from flowing from LX_ to OUT_ while the IC is shut down
by reversing the internal body diode of the p-channel
MOSFET. This feature is also active during track/ATM to
allow current limit to function as anticipated.
Upon leaving boost mode, the p-channel MOSFET
continues to prevent current from flowing from OUT_ to
LX_ until OUT_ and IN are approximately the same volt-
age. After this condition has been met, track/ATM and
shutdown operate normally.
Table 1. Modes of Operation
X = Don't care.
VIN COMPARATOR EN TREN MODE OF OPERATION
X 0 0 True Shutdown
X 0 1 Track
0 1 X Boost
1 1 X ATM
______________________________________________________________________________________ 13
MAX8969
Step-Up Converter
for Handheld Applications
Thermal Considerations
In most applications, the IC does not dissipate much
heat due to its high efficiency. But in applications where
the IC runs at high ambient temperature with heavy
loads, the heat dissipated may cause the temperature to
exceed the maximum junction temperature of the part. If
the junction temperature reaches approximately +165NC,
the thermal overload protection is activated.
The maximum power dissipation depends on the
thermal resistance of the IC package and circuit board.
The power dissipated (PD) in the device is:
PD = POUT x (1/E - 1)
where E is the efficiency of the converter and POUT is
the output power of the step-up converter. The maximum
allowed power dissipation is:
PMAX = (TJMAX - TA)/BJA
where (TJMAX - TA) is the temperature difference between
the IC’s maximum rated junction temperature and the
surrounding air, and BJA is the thermal resistance of
the junction through the PCB, copper traces, and other
materials to the surrounding air.
Applications Information
Step-Up Inductor Selection
Due to the small size of the recommended capacitor, the
inductor’s value is limited to approximately 1FH. Inductors
of approximately 1FH guarantee stable operation of the
converter with capacitance as small as 8FF (actual) pres-
ent on the converter’s output. If the inductor’s value is
reduced significantly below 1FH, ripple can become
excessive.
Output Capacitor Selection
An output capacitor (COUT) is required to keep the
output-voltage ripple small and to ensure regulation loop
stability. The output capacitor must have low imped-
ance at the switching frequency. Ceramic capacitors
are highly recommended due to their small size and low
ESR. Ceramic capacitors with X5R or X7R temperature
characteristics generally perform well. One 22FF (with
a minimum actual capacitance of 6FF under operating
conditions) is recommended. This capacitor along with
an additional 10FF of bypass capacitance, associated
with the load, guarantee proper performance of the IC.
The minimum combined capacitance is required to be
8FF or larger. These capacitors can be found with case
size 0603 or larger.
Input Capacitor Selection
The input capacitor (CIN) reduces the current peaks
drawn from the battery or input power source. The
impedance of CIN at the switching frequency should
be kept very low. Ceramic capacitors with X5R or X7R
temperature characteristics are highly recommended
due to their small size, low ESR, and small temperature
coefficients. Note that some ceramic dielectrics exhibit
large capacitance and ESR variation with temperature
and DC bias. Ceramic capacitors with Z5U or Y5V
temperature characteristics should be avoided. A 4.7FF
input capacitor is recommended for most applications.
This assumes that the input power source has at least
22FF of additional capacitance near the IC. For optimum
noise immunity and low input-voltage ripple, the input
capacitor value can be increased.
Recommended PCB Layout and Routing
Poor layout can affect the IC performance, causing
electromagnetic interference (EMI) and electromagnetic
compatibility (EMC) performance, ground bounce, and
voltage losses. Poor layout can also affect regulation
and stability.
A good layout is implemented using the following rules:
• Place the inductor, input capacitor, and output
capacitor close to the IC using short traces. These
components carry high switching frequencies and
large traces act like antennas. The output capacitor
placement is the most important in the PCB layout
and should be placed directly next to the IC. The
inductor and input capacitor placement are second-
ary to the output capacitor’s placement but should
remain close to the IC.
• Route the output voltage path away from the induc-
tor and LX_ switching node to minimize noise and
magnetic interference.
• Maximize the size of the ground metal on the com-
ponent side to help with thermal dissipation. Use a
ground plane with several vias connecting to the
component-side ground to further reduce noise
interference on sensitive circuit nodes.
Refer to the MAX8969 Evaluation Kit for more details.
Chip Information
PROCESS: BiCMOS
14 _____________________________________________________________________________________
MAX8969
Step-Up Converter
for Handheld Applications
Package Information
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.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.
E
D
AAAA
PIN 1
INDICATOR
MARKING
A3
A2
A1
A
See Note 7
0.05
S
S
e
D1
E1
b
SE
SD
0.05
M S
AB
A
B
SIDE VIEW
A
TOP VIEW
BOTTOM VIEW
A
1
1
PACKAGE OUTLINE
9 BUMPS, WLP PKG. 0.4mm PITCH
21-0459
D
0.64
0.19
0.45
0.025
0.27
0.80
0.80
0.40
0.00
0.00
W91F1+1
1.45 1.36
32
B
C
W91B1+7
W91C1+1
1.42
1.22
1.56 1.63
1.30
1.33
1.38
1.22
1.45
1.30
W91G1+1
1.45 1.48 1.44 1.47
TITLE
DOCUMENT CONTROL NO.
REV.
1
1
APPROVAL
COMMON DIMENSIONS
A
A2
A1
A3
b
E1
D1
e
SD
SE
0.05
0.03
0.03
BASIC
REF
BASIC
MIN
MAX MAX
MIN
E
D
PKG. CODE
DEPOPULATED
BUMPS
NONE
NOTES:
1. Terminal pitch is defined by terminal center to center value.
2. Outer dimension is defined by center lines between scribe lines.
3. All dimensions in millimeter.
4. Marking shown is for package orientation reference only.
5. Tolerance is ± 0.02 unless specified otherwise.
6. All dimensions apply to PbFree (+) package codes only.
7. Front - side finish can be either Black or Clear.
BASIC
BASIC
- DRAWING NOT TO SCALE -
NONE
NONE
NONE
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
9 WLP W91B1+7 21-0459 Refer to Application Note 1891
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 15
© 2012 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX8969
Step-Up Converter
for Handheld Applications
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 9/11 Initial release —
1 5/12 Updated Electrical Characteristics table 2
