_______________________________________________________________ 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.
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
19-5132; Rev 3; 11/10
General Description
The MAX15059 constant-frequency pulse-width modu-
lating (PWM) step-up DC-DC converter features an
internal switch and a high-side current monitor with high-
speed adjustable current limiting. This device is capable
of generating output voltages up to 76V (300mW for
the MAX15059A and 200mW for the MAX15059B) and
provides current monitoring up to 4mA. The MAX15059
operates from 2.8V to 5.5V.
The constant-frequency (400kHz) current-mode PWM
architecture provides low-noise-output voltage that is
easy to filter. A high-voltage internal power MOSFET
allows this device to boost output voltages up to 76V.
Internal soft-start circuitry limits the input current when
the boost converter starts. The MAX15059 features a
shutdown mode to save power.
The MAX15059 includes a current monitor with more
than three decades of dynamic range and monitors
current ranging from 500nA to 4mA with high accuracy.
Resistor-adjustable current limiting protects the APD
from optical power transients. A clamp diode protects
the monitor’s output from overvoltage conditions. Other
protection features include cycle-by-cycle current limit-
ing of the boost converter switch, undervoltage lockout
(UVLO), and thermal shutdown if the die temperature
reaches +125NC.
The MAX15059 is available in a thermally enhanced,
lead-free, 16-pin TQFN-EP package and operates over
the -40NC to +125NC temperature range.
Features
S Input Voltage Range: +2.8V to +5.5V
S Wide Output-Voltage Range from (VIN + 5V) to 76V
S Internal 1I (typ) 80V MOSFET
S Boost Converter Output Power: 300mW
S 200mW Version Available for Smaller Inductor
S Accurate ±5% (1:1 and 5:1) High-Side Current
Monitor
S Resistor-Adjustable Ultra-Fast APD Current Limit
(1µs Response Time)
S Open-Drain Current-Limit Indicator Flag
S 400kHz Fixed-Switching Frequency
S Constant PWM Frequency Provides Easy Filtering
in Low-Noise Applications
S Internal Soft-Start
S 2µA (max) Shutdown Current
S -40NC to +125NC Temperature Range
S Small, Thermally Enhanced, 3mm x 3mm, Lead-
Free, 16-Pin TQFN-EP Package
Applications
Avalanche Photodiode Biasing and Monitoring
PIN Diode Bias Supply
Low-Noise Varactor Diode Bias Supply
FBON Modules
GPON Modules
Ordering Information
Typical Operating Circuit
Note: The MAX15059AATE+ and MAX15059BATE+ operate over
the -40°C to +125°C temperature range. The MAX15059EATE+
and MAX15059BETE+ operate over the -40°C to +85°C tem-
perature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
EVALUATION KIT
AVAILABLE
CNTRL
IN
SGND
LX
RLIM
RLIM
2.87kI
RMOUT
1kI
VIN = 2.8V
TO 5.5V
CIN
1µF COUT
0.1µF
L1
4.7µH VOUT
DAC
CLAMP
CMOUT
OPTIONAL
(10nF)
MOUT
ILIM
SHDN
VDD
GPIO
GPIO
FB
BIAS
PGND
R2
348kI
R1
6.34kI
RADJ
(76V MAX)
APD ADC
D1
VDD
APD
µC
MAX15059
TIA
PART
MAXIMUM
POWER
(mW)
IAPD:
IMOUT
PIN-
PACKAGE
MAX15059AETE+ 300 1:1 16 TQFN-EP*
MAX15059BETE+ 200 5:1 16 TQFN-EP*
MAX15059AATE+ 300 1:1 16 TQFN-EP*
MAX15059BATE+ 200 5:1 16 TQFN-EP*
2 ______________________________________________________________________________________
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias 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, SHDN, FB, ILIM, RLIM, CNTRL to SGND ..........-0.3V to +6V
LX to PGND ...........................................................-0.3V to +80V
BIAS to SGND ......................................................-0.3V to +79V
APD, CLAMP to SGND ...........................-0.3V to (VBIAS + 0.3V)
PGND to SGND ....................................................-0.3V to +0.3V
MOUT to SGND .................................. -0.3V to (VCLAMP + 0.3V)
Continuous Power Dissipation (TA = +70NC)
16-Pin TQFN-EP (derate 20.8mW/NC above +70NC) ....1666.7mW
Operating Temperature Range
MAX15059AETE, MAX15059BETE ................. -40NC to +85NC
MAX15059AATE, MAX15059BATE .............. -40NC to +125NC
Operating Temperature Range .......................... -40NC to +85NC
Maximum Junction Temperature .....................................+150NC
Storage Temperature Range ............................ -65NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
ELECTRICAL CHARACTERISTICS
(VIN = VSHDN = VCNTRL= 3.3V. CIN = 1FF, VPGND = VSGND = 0V, VBIAS = 40V. LX = APD = CLAMP = ILIM = unconnected, VMOUT
= 0V, TA = -40NC to +85NC for the MAX15059AETE+ and MAX15059BETE+ and TA = -40NC to +125NC for the MAX15059AATE+ and
MAX15059BATE+, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
ABSOLUTE MAXIMUM RATINGS
Note 1: 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.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
TQFN
Junction-to-Ambient Thermal Resistance (qJA) ..........48°C/W
Junction-to-Case Thermal Resistance (qJC) .................7°C/W
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
INPUT SUPPLY
Supply Voltage Range VIN 2.8 5.5 V
Supply Current ISUPPLY VFB = 1.4V, no
switching
TA = -40°C to +85°C0.6 1.2 mA
TA = +125°C1.35
Undervoltage-Lockout
Threshold VUVLO VIN rising 2.475 2.6 2.775 V
Undervoltage-Lockout
Hysteresis VUVLO_HYS 200 mV
Shutdown Current ISHDN VSHDN = 0V 0.003 2 FA
Shutdown BIAS Current IBIAS_SHDN VBIAS = 3.3V, VSHDN = 0V 9 20 FA
BOOST CONVERTER
Output-Voltage Adjustment
Range VIN + 5 76 V
Switching Frequency fSW VIN = 5V 380 400 420 kHz
Maximum Duty Cycle DCLK VIN = 2.8V 88 90 92 %
FB Set-Point Voltage VFB_SET 1.205 1.23 1.255 V
FB Input-Bias Current IFB VFB = VFB_SET, TA = +25NC100 500 nA
Internal Switch On-Resistance RON ILX = 100mA,
VIN = 2.8V
TA = -40°C to +85°C1 2 W
TA = +125°C2.25
Peak Switch Current Limit ILIM_LX MAX15059A 1.1 1.2 1.3 A
MAX15059B 0.825 0.9 0.975
Peak Current-Limit Response 100 ns
_______________________________________________________________________________________ 3
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VSHDN = VCNTRL= 3.3V. CIN = 1FF, VPGND = VSGND = 0V, VBIAS = 40V. LX = APD = CLAMP = ILIM = unconnected, VMOUT
= 0V, TA = -40NC to +85NC for the MAX15059AETE+ and MAX15059BETE+ and TA = -40NC to +125NC for the MAX15059AATE+ and
MAX15059BATE+, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
LX Leakage Current VLX = 76V, TA = +25NC1FA
Line Regulation 2.8V P VIN P 5.5V, ILOAD = 4.5mA 0.01 %
Load Regulation 0 P ILOAD P 4.5mA 0.05 %
Soft-Start Duration 8 ms
Soft-Start Steps 32 Steps
CONTROL INPUT (CNTRL)
Maximum Control Input
Voltage Range FB set point is controlled to VCNTRL 1.2 V
CNTRL-to-REF Transition
Threshold VFB = VREF above this voltage 1.3 V
CNTRL Input-Bias Current VCNTRL = VFB_SET, TA = +25NC500 nA
CURRENT MONITOR
Bias Voltage Range VBIAS 10 76 V
Bias Quiescent Current IBIAS
IAPD = 500nA MAX15059A 150 250 FA
MAX15059B 150 250
IAPD = 2mA MAX15059A 4 6 mA
MAX15059B 3 4
Voltage Drop VDROP IAPD = 2mA, VDROP = VBIAS - VAPD 2.7 3.5 V
Dynamic Output Resistance at
MOUT RMOUT RMOUT = DVMOUT/DIMOUT,
IAPD = 2.5mA MAX15059A 5 GI
APD Current-Step Response Step load on IAPD = 20FA to 1mA 25 ns
MOUT Output Leakage APD is unconnected, TA = +25NC1 300 nA
Output Clamp Voltage VMOUT -
VCLAMP Forward diode current = 500µA 0.4 0.7 0.95 V
MOUT Voltage Range VMOUT 10V P VBIAS P 76V, 0 P IAPD P 1mA, CLAMP is
unconnected
VBIAS -
2.7 V
Current Gain IMOUT/IAPD
IAPD = 500nA MAX15059A 0. 95 1 1.1
mA/mA
MAX15059B 0.19 0.2 0.22
IAPD = 2mA MAX15059A 0.965 1 1.035
MAX15059B 0.193 0.2 0.207
Power-Supply Rejection Ratio PSRR
(DIMOUT/IMOUT)/DVBIAS,
VBIAS = 10V to 76V and
IAPD = 5FA to 1mA (Note 3)
MAX15059A 20 300 610
ppm/V
MAX15059B 20 300 700
APD Input Current Limit ILIM_APD TA = -40°C to +85°C4 4.6 5.2 mA
TA = +125°C3.85 5.2
Current-Limit Adjustment
Range 9.75kW ≥ RLIM ≥ 0 TA = -40°C to +85°C0.9 5.2 mA
TA = +125°C0.89 5.2
Power-Up Settling Time tS
IMOUT settles to within
0.1%, 10nF connected
from APD to ground
IAPD = 500nA 7.5 ms
IAPD = 2.5mA 90 Fs
4 ______________________________________________________________________________________
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Note 2: All MIN/MAX parameters are tested at TA = +25NC. Limits overtemperature are guaranteed by design.
Note 3: Guaranteed by design and not production tested.
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VSHDN = VCNTRL= 3.3V. CIN = 1FF, VPGND = VSGND = 0V, VBIAS = 40V. LX = APD = CLAMP = ILIM = unconnected, VMOUT
= 0V, TA = -40NC to +85NC for the MAX15059AETE+ and MAX15059BETE+ and TA = -40NC to +125NC for the MAX15059AATE+ and
MAX15059BATE+, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
Typical Operating Characteristics
(VIN = 3.3V, VOUT = 70V, TA = +25°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
LOGIC I/O
SHDN Input Voltage Low VIL 0.8 V
SHDN Input Voltage High VIH 2.1 V
ILIM Output Voltage Low VOL ILIM = 2mA 0.1 V
ILIM Output Leakage Current IOH TA = +25NC1FA
THERMAL PROTECTION
Thermal-Shutdown
Temperature Temperature rising +150 NC
Thermal-Shutdown Hysteresis 15 NC
EFFICIENCY vs. LOAD CURRENT
MAX15059 toc01
LOAD CURRENT (mA)
EFFICIENCY (%)
3.53.02.0 2.51.0 1.50.5
10
20
30
40
50
60
70
80
90
100
0
0 4.0
VOUT = 30V
VOUT = 70V
VOUT = 50V
VIN = 3.3V
EFFICIENCY vs. LOAD CURRENT
MAX15059 toc02
LOAD CURRENT (mA)
EFFICIENCY (%)
3.53.02.0 2.51.0 1.50.5
10
20
30
40
50
60
70
80
90
100
0
0 4.0
VOUT = 30V
VOUT = 70V
VOUT = 50V
VIN = 5V
MINIMUM STARTUP VOLTAGE
vs. LOAD CURRENT
MAX15059 toc03
LOAD CURRENT (mA)
MINIMUM STARTUP VOLTAGE (V)
3.53.02.0 2.51.0 1.50.5
2.56
2.57
2.58
2.59
2.60
2.61
2.62
2.63
2.64
2.65
2.55
0 4.0
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX15059 toc04
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
5.04.53.5 4.01.0 1.5 2.0 2.5 3.00.5
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0
0 5.5
VFB = 1.4V
TA = +125°C
TA = +85°C
TA = +25°C
TA = -40°C
NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX15059 toc05
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
5.04.54.03.53.0
20
40
60
80
100
0
2.5 5.5
TA = +125°C
TA = +85°C
TA = +25°C
TA = -40°C
_______________________________________________________________________________________ 5
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics (continued)
(VIN = 3.3V, VOUT = 70V, TA = +25°C, unless otherwise noted.)
LINE-TRANSIENT RESPONSE
MAX15059 toc11
VBIAS
(AC-COUPLED)
50mV/div
100µs/div
VIN
2V/div
3.3V
LOAD-TRANSIENT RESPONSE
MAX15059 toc10
VBIAS
(AC-COUPLED)
500mV/div
100µs/div
IAPD
2mA/div
0mA
HEAVY-LOAD SWITCHING WAVEFORMS
WITH RC FILTER
MAX15059 toc09
IL
1A/div
VLX
50V/div
VBIAS
(AC-COUPLED)
50mV/div
1µs/div
LIGHT-LOAD SWITCHING WAVEFORMS
WITH RC FILTER
MAX15059 toc08
IL
500mA/div
VLX
50V/div
VBIAS
(AC-COUPLED)
20mV/div
1µs/div
ENTERING SHUTDOWN
MAX15059 toc07
SHDN
2V/div
INDUCTOR
CURRENT
500mA/div
VOUT
50V/div
4ms/div
EXITING SHUTDOWN
MAX15059 toc06
SHDN
2V/div
INDUCTOR
CURRENT
500mA/div
VOUT
50V/div
1ms/div
6 ______________________________________________________________________________________
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics (continued)
(VIN = 3.3V, VOUT = 70V, TA = +25°C, unless otherwise noted.)
LX LEAKAGE CURRENT vs. TEMPERATURE
MAX15059 toc12
TEMPERATURE (°C)
LX LEAKAGE CURRENT (nA)
1109565 80-10 5 20 35 50-25
10
20
30
40
50
60
70
80
90
100
0
-40 125
CURRENT INTO LX PINS
VLX = 70V
LOAD REGULATION
MAX15059 toc13
LOAD CURRENT (mA)
REGULATION (%)
3.53.02.0 2.51.0 1.50.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
-0.5
0 4.0
MAXIMUM LOAD CURRENT
vs. SUPPLY VOLTAGE
MAX15059 toc14
SUPPLY VOLTAGE (V)
IOUT(MAX) (mA)
5.04.54.03.53.0
10
20
30
40
50
60
70
80
90
100
0
2.5 5.5
A: VOUT = 30V, B: VOUT = 35V, C: VOUT = 45V,
D: VOUT = 55V, E: VOUT = 60V, F: VOUT = 70V
A
F
E
D
B
C
BIAS CURRENT vs. BIAS VOLTAGE
(MAX15059A)
MAX15059 toc15
BIAS VOLTAGE (V)
BIAS CURRENT (mA)
70605040302010
0.1
1
10
0.01
0 80
IAPD = 2mA
IAPD = 500nA
BIAS CURRENT vs. BIAS VOLTAGE
(MAX15059B)
MAX15059 toc16
BIAS VOLTAGE (V)
BIAS CURRENT (mA)
70605040302010
0.1
1
10
0.01
0 80
IAPD = 2mA
IAPD = 500nA
APD CURRENT (mA)
BIAS CURRENT (mA)
10.10.010.001
0.1
1
10
0.01
0.0001 10
BIAS CURRENT vs. APD CURRENT
(MAX15059A)
MAX15059 toc17
VBIAS = 70V
BIAS CURRENT vs. APD CURRENT
(MAX15059B)
MAX15059 toc18
APD CURRENT (mA)
BIAS CURRENT (mA)
10.10.010.001
0.1
1
10
0.01
0.0001 10
VBIAS = 70V
BIAS CURRENT vs. TEMPERATURE
(MAX15059A)
MAX15059 toc19
TEMPERATURE (°C)
BIAS CURRENT (mA)
1109580655035205-10-25
1
10
0.1
-40 125
IAPD = 2mA
IAPD = 500nA
BIAS CURRENT vs. TEMPERATURE
(MAX15059B)
MAX15059 toc20
TEMPERATURE (°C)
BIAS CURRENT (mA)
1109580655035205-10-25
1
10
0.1
-40 125
IAPD = 2mA
IAPD = 500nA
_______________________________________________________________________________________ 7
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics (continued)
(VIN = 3.3V, VOUT = 70V, TA = +25°C, unless otherwise noted.)
APD TRANSIENT RESPONSE
(MAX15059A)
MAX15059 toc28
10ns/div
IAPD
1mA/div
0mA
IMOUT
2mA/div
0mA
APD TRANSIENT RESPONSE
(MAX15059A)
MAX15059 toc27
VAPD
(AC-COUPLED)
2V/div
20µs/div
IAPD
2mA/div
0mA
IMOUT
2mA/div
0mA
GAIN ERROR vs. BIAS VOLTAGE
(MAX15059B)
MAX15059 toc26
BIAS VOLTAGE (V)
GAIN ERROR (%)
706040 503020
-1.6
-1.2
-0.8
-0.4
0
0.4
0.8
1.2
1.6
2.0
-2.0
10 80
IAPD = 2mA
IAPD = 500µA
IAPD = 5µA
IAPD = 50µA
IAPD = 0.5µA
GAIN ERROR vs. BIAS VOLTAGE
(MAX15059A)
MAX15059 toc25
BIAS VOLTAGE (V)
GAIN ERROR (%)
706040 503020
-1.6
-1.2
-0.8
-0.4
0
0.4
0.8
1.2
1.6
2.0
-2.0
10 80
IAPD = 2mA
IAPD = 500µA
IAPD = 5µA
IAPD = 50µA
IAPD = 0.5µA
GAIN ERROR vs. TEMPERATURE
(MAX15059B)
MAX15059 toc24
TEMPERATURE (°C)
GAIN ERROR (%)
1109565 80-10 5 20 35 50-25
-1.6
-1.2
-0.8
-0.4
0
0.4
0.8
1.2
1.6
2.0
-2.0
-40 125
IAPD = 2mA
IAPD = 500µA
IAPD = 5µA
IAPD = 50µA
IAPD = 0.5µA
GAIN ERROR vs. TEMPERATURE
(MAX15059A)
MAX15059 toc23
TEMPERATURE (°C)
GAIN ERROR (%)
1109565 80-10 5 20 35 50-25
-1.6
-1.2
-0.8
-0.4
0
0.4
0.8
1.2
1.6
2.0
-2.0
-40 125
IAPD = 2mA
IAPD = 500µA
IAPD = 5µA
IAPD = 50µA
IAPD = 0.5µA
GAIN ERROR vs. APD CURRENT
(MAX15059B)
MAX15059 toc22
IAPD (µA)
GAIN ERROR (%)
1000100101
-4
-3
-2
-1
0
1
2
3
4
5
-5
0.1 10,000
VBIAS = 70V
GAIN ERROR vs. APD CURRENT
(MAX15059A)
MAX15059 toc21
IAPD (µA)
GAIN ERROR (%)
1000100101
-4
-3
-2
-1
0
1
2
3
4
5
-5
0.1 10,000
VBIAS = 70V
8 ______________________________________________________________________________________
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics (continued)
(VIN = 3.3V, VOUT = 70V, TA = +25°C, unless otherwise noted.)
STARTUP DELAY
MAX15059 toc29
IMOUT
500nA/div
VBIAS
50V/div
2ms/div
SHDN
5V/div
VBIAS = 70V,
IAPD = 500nA
STARTUP DELAY
MAX15059 toc30
1ms/div
IMOUT
1mA/div
VBIAS
50V/div
SHDN
5V/div
VBIAS = 70V,
IAPD = 2mA
STARTUP DELAY
MAX15059 toc31
IMOUT
500nA/div
VBIAS
5V/div
200µs/div
SHDN
5V/div
VBIAS = 10V,
IAPD = 500nA
STARTUP DELAY
MAX15059 toc32
400µs/div
IMOUT
1mA/div
VBIAS
5V/div
SHDN
5V/div
SHORT-CIRCUIT RESPONSE
MAX15059 toc33
2µs/div
IMOUT
2mA/div
VILIM
5V/div
VAPD
50V/div
RLIM = 3.16kI
VOLTAGE DROP vs. APD CURRENT
MAX15059 toc34
IAPD (µA)
VBIAS - VAPD (V)
1000100101
0.5
1.0
1.5
2.0
2.5
3.0
0
0.1 10,000
TA = +125°C
TA = +85°C
TA = +25°C
TA = -40°C
_______________________________________________________________________________________ 9
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Typical Operating Characteristics (continued)
(VIN = 3.3V, VOUT = 70V, TA = +25°C, unless otherwise noted.)
APD OUTPUT RIPPLE VOLTAGE
(0.1µF FROM APD TO GROUND, VBIAS = 70V, IAPD = 1mA)
MAX15059 toc39
1µs/div
VAPD
AC-COUPLED, 70V
1mV/div
FB SET POINT vs. TEMPERATURE
MAX15059 toc38
TEMPERATURE (°C)
FB SET POINT (V)
1109565 80-10 5 20 35 50-25
1.212
1.214
1.216
1.218
1.220
1.222
1.224
1.226
1.228
1.230
1.210
-40 125
VIN = 3.3V
SWITCHING FREQUENCY AND
DUTY CYCLE vs. LOAD CURRENT
MAX15059 toc37
LOAD CURRENT (mA)
SWITCHING FREQUENCY (kHz)
DUTY CYCLE (%)
3.53.02.0 2.51.0 1.50.50 4.0
392
394
396
398
400
402
404
406
408
410
390
5
10
15
20
25
30
35
40
45
50
0
DUTY CYCLE
SWITCHING FREQUENCY
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
MAX15059 toc36
INPUT VOLTAGE (V)
5.0
4.54.03.53.02.5 5.5
SWITCHING FREQUENCY (kHz)
392
394
396
398
400
402
404
406
408
410
390
SWITCHING FREQUENCY vs. TEMPERATURE
MAX15059 toc35
TEMPERATURE (°C)
FREQUENCY (kHz)
1109565 80-10 5 20 35 50-25
396
397
398
399
400
401
402
403
404
405
395
-40 125
10 _____________________________________________________________________________________
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Pin Description
Pin Configuration
15
16
14
13
6
5
7
IN
SGND
PGND
EP
CLAMP
RLIM
APD
1 2
LX
4
12 11 9
LX
PGND
SGND
ILIM
CNTRL
FB
MAX15059
SHDN MOUT
3
10
BIAS
TQFN
+
TOP VIEW
8
PIN NAME FUNCTION
1, 16 PGND Power Ground. Connect the negative terminals of the input and output capacitors to PGND. Connect
PGND externally to SGND at a single point, typically at the return terminal of the output capacitor.
2 IN Input-Supply Voltage. Bypass IN to PGND with a ceramic capacitor of 1FF minimum value.
3SHDN
Active-Low Shutdown Control Input. Apply a logic-low voltage to SHDN to shut down the device.
Connect SHDN to IN for normal operation. Ensure that VSHDN is not greater than the input voltage, VIN.
SHDN is internally pulled low. The converter is disabled when SHDN is left unconnected.
4, 8 SGND Signal Ground. Connect directly to the local ground plane. Connect SGND to PGND at a single point,
typically near the return terminal of the output capacitor.
5 FB
Feedback Regulation Input. Connect FB to the center tap of a resistive voltage-divider from the boost
output to SGND to set the output voltage. The FB voltage regulates to 1.23V (typ) when VCNTRL is
above 1.3V (typ) and to VCNTRL when VCNTRL is below 1.2V (typ).
6 CNTRL
Control Input for Boost Converter Output-Voltage Programmability. CNTRL allows the feedback set-point
voltage to be set externally by CNTRL when VCNTRL is less than 1.2V. Pull CNTRL above 1.3V (typ) to
use the internal 1.23V (typ) feedback set-point voltage.
7ILIM Open-Drain Current-Limit Indicator. ILIM asserts low when the APD current limit has been exceeded.
9 RLIM Current-Limit Resistor Connection. Connect a resistor from RLIM to SGND to program the APD current-
limit threshold. When RLIM is connected to SGND, the current limit is set to 4.6mA.
10 MOUT Current-Monitor Output. For the MAX15059A, MOUT sources a current equal to IAPD. For the
MAX15059B, MOUT sources a current equal to 1/5 of IAPD.
11 CLAMP Clamp Voltage Input. CLAMP is the external potential used for voltage clamping of MOUT.
______________________________________________________________________________________ 11
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Pin Description (continued)
Functional Diagram
PIN NAME FUNCTION
12 APD Reference Current Output. APD provides the source current to the cathode of the photodiode.
13 BIAS
Bias-Voltage Input. Connect BIAS to the boost converter output (VOUT) either directly or through a
lowpass filter for ripple attenuation. BIAS provides the voltage bias for the current monitor and is the
current source for APD.
14, 15 LX Drain of Internal 80V n-Channel DMOS. Connect inductor to LX. Minimize the trace area at LX to reduce
switching-noise emission.
— EP Exposed Pad. Connect to a large copper plane at the SGND and PGND potential to improve thermal
dissipation. Do not use as the only ground connection.
OSCILLATOR
400kHz
SHDN
FB
LX
80V
DMOS
PGND
CLAMP
MOUT
RLIM
APD
ILIM
1X
1X (A)
5X (B)
VREF
SGND
CNTRL
REFERENCE
COMPARATOR
-A
+A
-C
+C
MUX
SOFT-
START
SWITCH
CONTROL
LOGIC
CONTROL
MONITOR
SWITCH
CURRENT
SENSE
CURRENT-
LIMIT
ADJUSTMENT
CURRENT
LIMIT
UVLO
BIAS
AND REF
VREF
PEAK
CURRENT-LIMIT
COMPARATOR
IN
VREF
CLK
THERMAL
SHUTDOWN
BIAS
MAX15059
OUTPUT ERROR
AND CURRENT COMPARATOR
12 _____________________________________________________________________________________
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Detailed Description
The MAX15059 constant-frequency, current-mode, PWM
boost converters are intended for low-voltage systems
that require a locally generated high voltage. This device
is capable of generating a low-noise, high output volt-
age required for PIN and varactor diode biasing. The
MAX15059 operates from +2.8V to +5.5V.
The MAX15059 operates in discontinuous mode in
order to reduce the switching noise caused by reverse
recovery charge of the rectifier diode and eliminates
the need for external compensation components. Other
continuous-mode boost converters generate large volt-
age spikes at the output when the LX switch turns on
because there is a conduction path between the output,
diode, and switch to ground during the time needed
for the diode to turn off and reverse its bias voltage. To
reduce the output noise even further, the LX switch turns
off by taking 10ns typically to transition from on to off.
As a consequence, the positive slew rate of the LX node
is reduced and the current from the inductor does not
“force” the output voltage as hard as would be the case
if the LX switch were to turn off faster.
The constant-frequency (400kHz) PWM architecture
generates an output voltage ripple that is easy to filter.
An 80V lateral DMOS device used as the internal power
switch is ideal for boost converters with output voltages
up to 76V. The MAX15059 can also be used in other
topologies where the PWM switch is grounded, like
SEPIC and flyback converters.
The MAX15059 includes a versatile current monitor
intended for monitoring the APD, PIN, or varactor
diode DC current in fiber and other applications. The
MAX15059 features more than three decades of dynam-
ic current ranging from 500nA to 4mA and provides an
output current accurately proportional to the APD current
at MOUT. MOUT output accuracy is Q10% from 500nA to
1mA and Q5% from 1mA to 2mA.
The MAX15059 also features a shutdown logic input to
disable the device and reduce its standby current to 2FA
(max).
Fixed-Frequency PWM Controller
The heart of the MAX15059 current-mode PWM control-
ler is a BiCMOS multi-input comparator that simulta-
neously processes the output-error signal and switch
current signal. The main PWM comparator uses direct
summing, lacking a traditional error amplifier and its
associated phase shift. The direct summing configura-
tion approaches ideal cycle-by-cycle control over the
output voltage since there is no conventional error ampli-
fier in the feedback path.
This device operates in PWM mode using a fixed-
frequency, current-mode operation. The current-mode
frequency loop regulates the peak inductor current as a
function of the output-voltage error signal.
The current-mode PWM controller is intended for DCM
operation. No internal slope compensation is added to
the current signal.
Current Limit
The current limit of the current monitor is programmable
from 1mA to 4.6mA (typ). Connect RLIM to SGND to get
a default current-limit threshold of 4.6mA or connect a
resistor from RLIM to SGND to program the current-limit
threshold below the default setting of 4.6mA. Calculate
the value of the external resistor, RLIM, for a given cur-
rent limit, ILIM, using the following equation:
LIM LIM
1.23V
R (k ) x10 2.67(k )
I (mA)
W = − W
Clamping the Monitor Output Voltage
(MOUT)
CLAMP provides a means for diode clamping the volt-
age at MOUT; thus, VMOUT is limited to (VCLAMP + 0.6V).
CLAMP can be connected to either an external supply or
BIAS. Leave CLAMP unconnected if voltage clamping is
not required.
Shutdown
The MAX15059 features an active-low shutdown input
(SHDN). Pull SHDN low or leave it unconnected to enter
shutdown. During shutdown, the supply current drops
to 2FA (max). The output remains connected to the
input through the inductor and output rectifier, holding
the output voltage to one diode drop below IN when
the MAX15059 is in shutdown. Connect SHDN to IN for
always-on operation.
Adjusting the Feedback
Set-Point/Reference Voltage
Apply a voltage to the CNTRL input to set the feedback
set-point reference voltage, VREF (see the Functional
Diagram). For VCNTRL > 1.3V, the internal 1.23V (typ)
reference voltage is used as the feedback set point and
for VCNTRL < 1.2V, the CNTRL voltage is used as the
reference voltage (VFB set equal to VCNTRL).
______________________________________________________________________________________ 13
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Design Procedure
Setting the Output Voltage
Set the MAX15059 output voltage by connecting a resis-
tive divider from the output to FB to SGND (Figure 1).
Select R1 (FB to SGND resistor) between 5kI and 10kI.
Calculate R2 (V
OUT to FB resistor) using the following
equation:
OUT
2 1 REF
V
R R 1
V
= −
where VOUT can range from (VIN + 5V) to 76V. Apply a
voltage to the CNTRL input to set the feedback set-point
reference voltage, VREF (see the Functional Diagram).
For VCNTRL > 1.3V, the internal 1.23V (typ) reference
voltage is used as the feedback set point and for VCNTRL
< 1.2V, VREF = VCNTRL. See the Adjusting the Feedback
Set-Point/Reference Voltage section for more information
on adjusting the feedback reference voltage, VREF.
Determining Peak Inductor Current
If the boost converter remains in the discontinuous mode
of operation, then the approximate peak inductor cur-
rent, ILPEAK (in A), is represented by the formula below:
S OUT IN_MIN OUT_MAX
LPEAK
2 t (V V ) I
IL
× × − ×
=η×
where tS is the switching period in Fs, VOUT is the output
voltage in volts, VIN_MIN is the minimum input voltage
in volts, IOUT_MAX is the maximum output current in
amps, L is the inductor value in FH, and E is the effi-
ciency of the boost converter (see the Typical Operating
Characteristics).
Determining the Inductor Value
Three key inductor parameters must be specified for
operation with the MAX15059: inductance value (L),
inductor saturation current (ISAT), and DC resistance
(DCR). In general, the inductor should have a saturation
current rating greater than the maximum peak switch
current-limit value (ILIM_LX = 1.3A). DCR should be be
low for reasonable efficiency.
Use the following formula to calculate the lower bound of
the inductor value at different output voltages and output
currents. This is the minimum inductance value for dis-
continuous mode operation for supplying full 300mW of
output power:
S OUT OUT IN_MIN
MIN 2
LIM_LX
2 t I (V V )
L [ H]
I
× × × −
µ = η×
where VIN_MIN, VOUT (both in volts), and IOUT (in amps)
are typical values (so that efficiency is optimum for typi-
cal conditions), tS (in Fs) is the period, E is the efficiency,
and ILIM_LX is the peak switch current in amps (see the
Electrical Characteristics table).
Calculate the optimum value of L (LOPTIMUM) to ensure
the full output power without reaching the boundary
between continuous-conduction mode (CCM) and dis-
continuous-conduction mode (DCM) using the following
formula:
MAX
OPTIMUM
L [ H]
L [ H] 2.25
µ
µ =
where:
2OUT IN_MIN S
IN_MIN
MAX 2
OUT OUT
V (V V ) t
L [ H]
2 I V
− × × η
µ = × ×
For a design in which VIN = 3.3V, VOUT = 70V, IOUT =
3mA, E = 45%, ILIM_LX = 1.2A, and tS = 2.5Fs: LMAX =
27FH and LMIN = 1.5FH.
For a worse-case scenario in which VIN = 2.8V, VOUT
= 70V, IOUT = 4mA, η = 43%, ILIM_LX = 1.2A, and tS =
2.5Fs: LMAX = 15FH and LMIN = 2.2FH.
The choice of 4.7FH is reasonable given the worst-case
scenario above. In general, the higher the inductance,
the lower the switching noise. Load regulation is also
better with higher inductance.
Figure 1. Adjustable Output Voltage
VCNTRL > 1.3V, VFB = 1.23V
VCNTRL < 1.2V, VFB = VCNTRL
FB
R2
R1
MAX15059
VOUT
14 _____________________________________________________________________________________
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Diode Selection
The MAX15059’s high switching frequency demands a
high-speed rectifier. Schottky diodes are recommended
for most applications because of their fast recovery time
and low forward-voltage drop. Ensure that the diode’s
peak current rating is greater than the peak inductor cur-
rent. Also, the diode breakdown voltage must be greater
than VOUT.
Output Filter Capacitor Selection
For most applications, use a small output capacitor of
0.1FF or greater. To achieve low output ripple, a capaci-
tor with low ESR, low ESL, and high capacitance value
should be selected. If tantalum or electrolytic capacitors
are used to achieve high capacitance values, always
add a smaller ceramic capacitor in parallel to bypass the
high-frequency components of the diode current. The
higher ESR and ESL of electrolytic capacitors increase
the output ripple and peak-to-peak transient voltage.
Assuming the contribution from the ESR and capacitor
discharge equals 50% (proportions may vary), calculate
the output capacitance and ESR required for a specified
ripple using the following equations:
[ ]
OUT LPEAK OPTIMUM
OUT S
OUT OUT IN_MIN
OUT
OUT
I I x L
C [ F] t
0.5 x V (V V )
0.5 x V
ESR m I
µ = −
∆ −
∆
W =
For very-low-output-ripple applications, the output of the
boost converter can be followed by an RC filter to further
reduce the ripple. Figure 2 shows a 100I, 0.1FF (RF
CF) filter used to reduce the switching output ripple to
1mVP-P with a 0.1mA load or 1mVP-P with a 4mA load.
The output voltage regulation resistive divider must
remain connected to the diode/output capacitor node.
Use X7R ceramic capacitors for more stability over the
full temperature range.
Input-Capacitor Selection
Bypass IN to PGND with a 1FF (min) ceramic capacitor.
Depending on the supply source impedance, higher val-
ues may be needed. Make sure that the input capacitors
are close enough to the IC to provide adequate decou-
pling at IN as well. If the layout cannot achieve this,
add another 0.1FF ceramic capacitor between IN and
PGND in the immediate vicinity of the IC. Bulk aluminum
electrolytic capacitors may be needed to avoid chatter-
ing at low-input voltage. In case of aluminum electrolytic
capacitors, calculate the capacitor value and ESR of the
input capacitor using the following equations:
[ ]
OUT OUT LPEAK OPTIMUM OUT
IN S
IN_MIN IN IN_MIN OUT IN_MIN
IN IN_MIN
OUT OUT
V x I I x L x V
C [ F] t
x V x 0.5 x V V (V V )
0.5x V x x V
ESR m V x I
µ = −
η ∆ −
∆ η
W =
Figure 2. Typical Operating Circuit with RC Filter
CNTRL
SHDN
IN
SGND
VIN = 2.8V
TO 5.5V
PGND
CIN
L1
CIN
FB
BIAS
LX VOUT
R2
R1
COUT
CF
D1 RF
MAX15059
______________________________________________________________________________________ 15
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Applications Information
Using APD or PIN Photodiodes
in Fiber Applications
When using the MAX15059 to monitor APD or PIN photo-
diode currents in fiber applications, several issues must
be addressed. In applications where the photodiode
must be fully depleted, keep track of voltages budgeted
for each component with respect to the available supply
voltage(s). The current monitors require as much as 3.5V
between BIAS and APD, which must be considered part
of the overall voltage budget.
Additional voltage margin can be created if a nega-
tive supply is used in place of a ground connection,
as long as the overall voltage drop experienced by
the MAX15059 is less than or equal to 76V. For this
type of application, the MAX15059 is suggested so the
output can be referenced to “true” ground and not the
negative supply. The MAX15059’s output current can
be referenced as desired with either a resistor to ground
or a transimpedance amplifier. Take care to ensure
that output voltage excursions do not interfere with the
required margin between BIAS and MOUT. In many fiber
applications, MOUT is connected directly to an ADC
that operates from a supply voltage that is less than the
voltage at BIAS. Connecting the MAX15059’s clamping
diode output, CLAMP, to the ADC power supply helps
avoid damage to the ADC. Without this protection, volt-
ages can develop at MOUT that might destroy the ADC.
This protection is less critical when MOUT is connected
directly to subsequent transimpedance amplifiers (linear
or logarithmic) that have low-impedance, near-ground-
referenced inputs. If a transimpedance amp is used on
the low side of the photodiode, its voltage drop must
also be considered. Leakage from the clamping diode
is most often insignificant over nominal operating condi-
tions, but grows with temperature.
To maintain low levels of wideband noise, lowpass filter-
ing the output signal is suggested in applications where
only DC measurements are required. Connect the filter
capacitor at MOUT. Determining the required filtering
components is straightforward, as the MAX15059 exhib-
its a very high output impedance of 5GI.
In some applications where pilot tones are used to identi-
fy specific fiber channels, higher bandwidths are desired
at MOUT to detect these tones. Consider the minimum
and maximum currents to be detected, then consult the
frequency response and noise typical operating curves.
If the minimum current is too small, insufficient band-
width could result, while too high a current could result in
excessive noise across the desired bandwidth.
Layout Considerations
Careful PCB layout is critical to achieve low switching
losses and clean and stable operation. Protect sensitive
analog grounds by using a star ground configuration.
Connect SGND and PGND together close to the device
at the return terminal of the output bypass capacitor. Do
not connect them together anywhere else. Keep all PCB
traces as short as possible to reduce stray capacitance,
trace resistance, and radiated noise. Ensure that the
feedback connection to FB is short and direct. Route
high-speed switching nodes away from the sensitive
analog areas. Use an internal PCB layer for SGND as an
EMI shield to keep radiated noise away from the device,
feedback dividers, and analog bypass capacitors. Refer
to the MAX15059 Evaluation Kit data sheet for a layout
example.
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns,
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.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
16 TQFN-EP T1633-4 21-0136 90-0031
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.
16 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX15059
76V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 1/10 Initial release —
1 3/10 Replaced five TOCs, added three TOCs, updated text 1, 2, 3, 5–8, 11
2 7/10 EC table specifications modified 2, 3
3 11/10 EC table extended to +125°C 1–8 , 14
