Datasheet

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General Description

The MAX15031 consists of a constant-frequency pulse-

width modulating (PWM) step-up DC-DC converter with

an internal switch and a high-side current monitor with

high-speed adjustable current limiting. This device can

generate output voltages up to 76V and provides current

monitoring up to 4mA (up to 300mW). The MAX15031

can be used for a wide variety of applications such as

avalanche photodiode biasing, PIN biasing, or varactor

biasing, and LCD displays. The MAX15031 operates

from 2.7V to 11V.

The constant-frequency (400kHz), current-mode PWM

architecture provides low-noise output voltage that is

easy to filter. A high-voltage, internal power switch

allows this device to boost output voltages up to 76V.

Internal soft-start circuitry limits the input current when

the boost converter starts. The MAX15031 features a

shutdown mode to save power.

The MAX15031 includes a current monitor with more

than three decades of dynamic range and monitors cur-

rent 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,

and thermal shutdown if the die temperature reaches

+160°C.

The MAX15031 is available in a thermally enhanced

4mm x 4mm, 16-pin TQFN package and operates over

the -40°C to +125°C automotive temperature range.

Applications

Avalanche Photodiode Biasing and Monitoring

PIN Diode Bias Supplies

Low-Noise Varactor Diode Bias Supplies

FBON Modules

GPON Modules

LCD Displays

Features

♦ Input Voltage Range

+2.7V to +5.5V (Using Internal Charge Pump) or

+5.5V to +11V

♦ Wide Output-Voltage Range from (V

+ 1V) to 76V

♦ Internal 1Ω (typ) 80V Switch

♦ 300mW Boost Converter Output Power

♦ Accurate ±10% (500nA to 1mA) and ±3.5% (1mA

to 4mA) High-Side Current Monitor

♦ Resistor-Adjustable Ultra-Fast APD Current Limit

(1µs Response Time)

♦ Open-Drain Current-Limit Indicator Flag

♦ 400kHz Fixed Switching Frequency

♦ Constant PWM Frequency Provides Easy Filtering

in Low-Noise Applications

♦ Internal Soft-Start

♦ 2µA (max) Shutdown Current

♦ -40°C to +125°C Temperature Range

♦ Small Thermally Enhanced, 4mm x 4mm, 16-Pin

TQFN Package

MAX15031

80V, 300mW Boost Converter and Current

Monitor for APD Bias Applications

________________________________________________________________

Maxim Integrated Products

PWR

CLAMP

RLIM

APD

SHDN

12 11 9

PGND

ILIM

CNTRL

SGND

CN MOUT

BIAS

THIN QFN

(4mm

4mm)

TOP VIEW

MAX15031

*EP

*EXPOSED PAD

Pin Configuration

Ordering Information

19-4299; Rev 2; 6/09

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.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE PIN-PACKAGE

MAX15031ATE+ -40°C to +125°C 16 TQFN-EP*

Denotes a lead(Pb)-free/RoHS-compliant package.

EP = Exposed pad.

Typical Operating Circuits appear at end of data sheet.

Summary of content (17 pages)

PAGE 1
9-4299; Rev 2; 6/09 KIT ATION EVALU E L B AVAILA 80V, 300mW Boost Converter and Current Monitor for APD Bias Applications Features The MAX15031 consists of a constant-frequency pulsewidth modulating (PWM) step-up DC-DC converter with an internal switch and a high-side current monitor with high-speed adjustable current limiting. This device can generate output voltages up to 76V and provides current monitoring up to 4mA (up to 300mW).
PAGE 2
MAX15031 80V, 300mW Boost Converter and Current Monitor for APD Bias Applications ABSOLUTE MAXIMUM RATINGS Continuous Power Dissipation 16-Pin TQFN (derate 25mW/°C above +70°C) ............2000mW Thermal Resistance (Note 1) θJA ....................................................................................40°C/W θJC ......................................................................................6°C/W Operating Temperature Range .........................-40°C to +125°C Junction Temperature ......
PAGE 3
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications (VIN = VPWR = 3.3V. VSHDN = 3.3V. CIN = CPWR = 10μF. CCP = 10nF, VCNTRL = VIN. VRLIM = 0. VPGND = VSGND = 0. VBIAS = 40V. APD = unconnected. CLAMP = unconnected. ILIM = unconnected, MOUT = unconnected. TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN Soft-Start Duration Soft-Start Steps (0.25 x ILIM_LX) to ILIM_LX TYP MAX UNITS 8 ms 32 Steps 1.
PAGE 4
Typical Operating Characteristics (VPWR = VIN = 3.3V, VOUT = 70V, circuit of Figure 3 (Figure 4 for VIN > 5.5V), unless otherwise noted.) 60 50 40 VOUT = 55V 30 VOUT = 70V 20 EFFICIENCY (%) 50 EFFICIENCY (%) 50 40 VOUT = 55V 30 VOUT = 70V 10 3 VOUT = 70V 4 1 0 2 3 1 0 4 2 3 4 LOAD CURRENT (mA) LOAD CURRENT (mA) LOAD CURRENT (mA) MINIMUM STARTUP VOLTAGE vs. LOAD CURRENT SUPPLY CURRENT vs. SUPPLY VOLTAGE NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE 2.53 2.52 2.51 2.
PAGE 5
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications MAX15031 Typical Operating Characteristics (continued) (VPWR = VIN = 3.3V, VOUT = 70V, circuit of Figure 3 (Figure 4 for VIN > 5.5V), unless otherwise noted.) LIGHT-LOAD SWITCHING WAVEFORM WITH RC FILTER HEAVY-LOAD SWITCHING WAVEFORM WITH RC FILTER MAX15031 toc09 MAX15031 toc10 IOUT = 0.
PAGE 6
Typical Operating Characteristics (continued) (VPWR = VIN = 3.3V, VOUT = 70V, circuit of Figure 3 (Figure 4 for VIN > 5.5V), unless otherwise noted.) 1 0.1 3 1 0.1 VBIAS = 70V 4 IAPD = 500nA MAX15031 toc19 5 2 GAIN ERROR (%) IAPD = 2mA BIAS CURRENT (mA) VBIAS = 70V MAX15031 toc18 10 MAX15031 toc17 10 GAIN ERROR vs. APD CURRENT BIAS CURRENT vs. TEMPERATURE BIAS CURRENT vs. APD CURRENT BIAS CURRENT (mA) 1 0 -1 -2 -3 -4 -5 0.01 0.001 0.01 0.1 IAPD = 500μA 0.80 IAPD = 5μA 0.60 0.
PAGE 7
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications STARTUP DELAY STARTUP DELAY MAX15031 toc24 MAX15031 toc25 VAPD 20V/div VAPD 2V/div 3V 0V IMOUT 50μA/div IAPD = 2mA IMOUT 20nA/div IAPD = 500nA VBIAS = 5V 0nA 100μs/div 0nA 100μs/div STARTUP DELAY SHORT-CIRCUIT RESPONSE MAX15031 toc26 MAX15031 toc27 ILIM 2V/div VBIAS 2V/div 0V 0V IBIAS 2mA/div IMOUT 50μA/div IAPD = 2mA VBIAS = 5V 0nA 40μs/div 40ms/div VOLTAGE DROP vs. APD CURRENT SWITCHING FREQUENCY vs.
PAGE 8
Typical Operating Characteristics (continued) (VPWR = VIN = 3.3V, VOUT = 70V, circuit of Figure 3 (Figure 4 for VIN > 5.5V), unless otherwise noted.) SWITCHING FREQUENCY AND DUTY CYCLE vs. LOAD CURRENT SWITCHING FREQUENCY vs. INPUT VOLTAGE 415 SWITCHING FREQUENCY (kHz) 460 440 420 400 380 360 340 40 405 30 400 SWITCHING FREQUENCY 395 20 390 10 0 380 2 4 6 8 10 0 12 1 2 4 3 INPUT VOLTAGE (V) LOAD CURRENT (mA) FB SET-POINT VARIATION vs.
PAGE 9
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications PIN NAME FUNCTION 1 PWR Boost Converter Input Voltage. PWR powers the switch driver and charge pump. Bypass PWR to PGND with a ceramic capacitor of 1μF minimum value. 2 CP Positive Terminal of the Charge-Pump Flying Capacitor for 2.7V to 5.5V Supply Voltage Operation. Connect CP to IN when the input voltage is in the 5.5V to 11V range. 3 CN Negative Terminal of the Charge-Pump Flying Capacitor for 2.7V to 5.
PAGE 10
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications MAX15031 Functional Diagram PWR FB -A VREF MUX CNTRL OUTPUT ERROR AND CURRENT COMPARATOR +A LX -C SGND +C PEAK CURRENT-LIMIT COMPARATOR SOFTSTART SWITCH CONTROL LOGIC 80V DMOS PGND REFERENCE COMPARATOR VREF SWITCH CURRENT SENSE CLAMP CN CP CHARGE PUMP (DOUBLER) THERMAL SHUTDOWN 1x VREF MAX15031 CURRENT MONITOR MOUT CURRENTLIMIT ADJUSTMENT RLIM CURRENT LIMIT APD BIAS AND REFERENCE IN UVLO 10x CLK ILIM OSCI
PAGE 11
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications The MAX15031 also features a shutdown logic input to disable the device and reduce its standby current to 2μA (max). Fixed-Frequency PWM Controller The heart of the MAX15031 current-mode PWM controller is a BiCMOS multiple-input comparator that simultaneously 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.
PAGE 12
MAX15031 80V, 300mW Boost Converter and Current Monitor for APD Bias Applications VOUT output current in amperes, L is the inductor value in microhenrys, and η is the efficiency of the boost converter (see the Typical Operating Characteristics). Determining the Inductor Value R2 FB MAX15031 R1 Three key inductor parameters must be specified for operation with the MAX15031: inductance value (L), inductor saturation current (ISAT), and DC resistance (DCR).
PAGE 13
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications 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 100Ω (RF), 0.1μF (CF) filter used to reduce the switching output ripple to 1mVP-P with a 0.1mA load or 2mVP-P with a 4mA load. The output-voltage regulation resistor-divider must remain connected to the diode and output capacitor node.
PAGE 14
MAX15031 80V, 300mW Boost Converter and Current Monitor for APD Bias Applications Determining Monitor Current Limit Calculate the value of the monitor current-limit resistor, RLIM, for a given APD current limit, ILIMIT, using the following equation: RLIM = 10 × 1.245V ILIMIT(mA) The RLIM resistor, RLIM, ranges from 12.45kΩ to 2.5Ω for APD currents from 1mA to 5mA.
PAGE 15
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications L1 4.7μH D1 VOUT (70V MAX) VIN COUT 0.1μF CPWR 1μF PWR RADJ CF 0.1μF LX CNTRL R2 348kΩ RF 100Ω R1 6.34kΩ PGND IN CIN 1μF BIAS FB MAX15031 CP GPIO SHDN CCP 10nF ILIM GPIO VDD CN VDD CLAMP RLIM RLIM 2.87kΩ SGND μC APD MOUT ADC APD RMOUT 10kΩ DAC CMOUT (OPTIONAL) Figure 3. Typical Operating Circuit for VIN = 2.7V to 5.
PAGE 16
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications MAX15031 Typical Operating Circuits (continued) L1 4.7μH VIN = 5.5V TO 11V D1 VOUT (70V MAX) COUT 0.1μF CPWR 1μF PWR CF 0.1μF LX CNTRL R2 348kΩ RF 100Ω R1 634kΩ PGND IN CIN 1μF BIAS FB CP MAX15031 GPIO SHDN ILIM CN GPIO VDD VDD CLAMP RLIM RLIM 2.87kΩ SGND μC APD MOUT ADC APD RMOUT 10kΩ DAC CMOUT (OPTIONAL) Figure 4. Typical Operating Circuit for VIN = 5.
PAGE 17
80V, 300mW Boost Converter and Current Monitor for APD Bias Applications REVISION REVISION NUMBER DATE 0 10/08 1 2 DESCRIPTION PAGES CHANGED Initial release. — 3/09 Updated Electrical Characteristics and added new Note 3. 3 6/09 • Changed “Shutdown Input Bias Current” to “BIAS Current During Shutdown” in the Electrical Characteristics table. • Changed minimum value for the Current Gain (IAPD = 2mA) specification to 0.0965 in the Electrical Characteristics table.