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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 (V

+ 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

SGND

RLIM

LIM

2.87kI

MOUT

1kI

= 2.8V

TO 5.5V

1µF

OUT

0.1µF

4.7µH

OUT

DAC

CLAMP

MOUT

OPTIONAL

(10nF)

MOUT

ILIM

SHDN

GPIO

BIAS

PGND

348kI

6.34kI

ADJ

(76V MAX)

APD

ADC

APD

µC

MAX15059

TIA

PART

MAXIMUM

POWER

(mW)

APD

MOUT

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*

Summary of content (16 pages)

PAGE 1
9-5132; Rev 3; 11/10 TION KIT EVALUA BLE A IL A V A 76V, 300mW Boost Converter and Current Monitor for APD Bias Applications Features The MAX15059 constant-frequency pulse-width modulating (PWM) step-up DC-DC converter features an internal switch and a high-side current monitor with highspeed 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.
PAGE 2
MAX15059 76V, 300mW Boost Converter and Current Monitor for APD Bias Applications ABSOLUTE MAXIMUM RATINGS 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............
PAGE 3
76V, 300mW Boost Converter and Current Monitor for APD Bias Applications (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 LX Leakage Current VLX = 76V, TA = +25NC Line Regulation 2.8V P VIN P 5.
PAGE 4
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 0.
PAGE 5
76V, 300mW Boost Converter and Current Monitor for APD Bias Applications EXITING SHUTDOWN ENTERING SHUTDOWN MAX15059 toc06 MAX15059 toc07 SHDN 2V/div SHDN 2V/div INDUCTOR CURRENT 500mA/div INDUCTOR CURRENT 500mA/div VOUT 50V/div VOUT 50V/div 1ms/div 4ms/div LIGHT-LOAD SWITCHING WAVEFORMS WITH RC FILTER HEAVY-LOAD SWITCHING WAVEFORMS WITH RC FILTER MAX15059 toc08 MAX15059 toc09 VBIAS (AC-COUPLED) 20mV/div VBIAS (AC-COUPLED) 50mV/div VLX 50V/div VLX 50V/div IL 500mA/div IL 1A/div 1µs/div
PAGE 6
Typical Operating Characteristics (continued) (VIN = 3.3V, VOUT = 70V, TA = +25°C, unless otherwise noted.) 0.3 60 50 40 0.1 0 -0.1 40 30 20 -0.3 20 10 -0.4 10 0 -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 B C 50 -0.2 0 A 60 30 D 3.0 2.5 4.0 3.5 E 4.0 4.5 F 5.0 TEMPERATURE (°C) LOAD CURRENT (mA) SUPPLY VOLTAGE (V) BIAS CURRENT vs. BIAS VOLTAGE (MAX15059A) BIAS CURRENT vs. BIAS VOLTAGE (MAX15059B) BIAS CURRENT vs. APD CURRENT (MAX15059A) 0.
PAGE 7
6V, 300mW Boost Converter and Current Monitor for APD Bias Applications 1 0 -1 VBIAS = 70V 3 GAIN ERROR (%) 2 4 2.0 2 1.6 1 0 -1 0.4 0 -3 -3 -1.2 -4 -4 -1.6 -5 -5 10 100 1000 10,000 -2.0 10,000 -40 -25 -10 5 20 35 50 65 80 95 110 125 GAIN ERROR vs. TEMPERATURE (MAX15059B) GAIN ERROR vs. BIAS VOLTAGE (MAX15059A) GAIN ERROR vs. BIAS VOLTAGE (MAX15059B) IAPD = 50µA IAPD = 0.5µA 0.8 IAPD = 5µA 0.4 0 IAPD = 500µA -0.4 IAPD = 2mA -0.8 -1.2 -1.2 -1.6 -1.6 -2.0 -2.
PAGE 8
Typical Operating Characteristics (continued) (VIN = 3.3V, VOUT = 70V, TA = +25°C, unless otherwise noted.
PAGE 9
76V, 300mW Boost Converter and Current Monitor for APD Bias Applications SWITCHING FREQUENCY vs. INPUT VOLTAGE SWITCHING FREQUENCY vs. TEMPERATURE MAX15059 toc36 403 408 SWITCHING FREQUENCY (kHz) 404 402 401 400 399 398 397 406 404 402 400 398 396 394 392 396 390 395 2.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 3.0 SWITCHING FREQUENCY AND DUTY CYCLE vs. LOAD CURRENT MAX15059 toc37 410 DUTY CYCLE 1.230 45 1.228 1.226 35 1.
PAGE 10
MAX15059 76V, 300mW Boost Converter and Current Monitor for APD Bias Applications CLAMP MOUT RLIM TOP VIEW APD Pin Configuration 12 11 10 9 BIAS 13 LX 14 MAX15059 LX 15 + 1 2 3 4 IN SHDN SGND EP PGND PGND 16 8 SGND 7 ILIM 6 CNTRL 5 FB TQFN Pin Description PIN NAME FUNCTION 1, 16 PGND 2 IN 3 SHDN Active-Low Shutdown Control Input. Apply a logic-low voltage to SHDN to shut down the device. Connect SHDN to IN for normal operation.
PAGE 11
76V, 300mW Boost Converter and Current Monitor for APD Bias Applications PIN NAME 12 APD Reference Current Output. APD provides the source current to the cathode of the photodiode. FUNCTION 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.
PAGE 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 voltage required for PIN and varactor diode biasing. The MAX15059 operates from +2.8V to +5.5V.
PAGE 13
76V, 300mW Boost Converter and Current Monitor for APD Bias Applications Setting the Output Voltage Set the MAX15059 output voltage by connecting a resistive divider from the output to FB to SGND (Figure 1). Select R1 (FB to SGND resistor) between 5kI and 10kI. Calculate R2 (VOUT to FB resistor) using the following equation:  V   R 2 = R1 OUT  − 1 V  REF   where VOUT can range from (VIN + 5V) to 76V.
PAGE 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 current. Also, the diode breakdown voltage must be greater than VOUT. VIN = 2.8V TO 5.
PAGE 15
76V, 300mW Boost Converter and Current Monitor for APD Bias Applications Using APD or PIN Photodiodes in Fiber Applications When using the MAX15059 to monitor APD or PIN photodiode 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.
PAGE 16
MAX15059 76V, 300mW Boost Converter and Current Monitor for APD Bias Applications Revision History REVISION NUMBER REVISION DATE DESCRIPTION 0 1/10 Initial release 1 3/10 Replaced five TOCs, added three TOCs, updated text 2 7/10 EC table specifications modified 3 11/10 EC table extended to +125°C PAGES CHANGED — 1, 2, 3, 5–8, 11 2, 3 1–8 , 14 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product.