10 _____________________________________________________________________________________

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 Paddle. 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)

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

PEAK

CURRENT-LIMIT

COMPARATOR

IN

CLK

THERMAL

SHUTDOWN

BIAS

MAX15059

OUTPUT ERROR

AND CURRENT COMPARATOR