Datasheet

MAX15031
80V, 300mW Boost Converter and Current
Monitor for APD Bias Applications
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Pin Description
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.
2CP
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.
3CN
Negative Terminal of the Charge-Pump Flying Capacitor for 2.7V to 5.5V Supply Voltage Operation. Leave CN
unconnected when the input voltage is in the 5.5V to 11V range.
4IN
Input Supply Voltage. IN powers all blocks of the MAX15031 except the switch driver and charge pump.
Bypass IN to PGND with a ceramic capacitor of 1μF minimum value.
5 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.
6FB
Feedback Regulation Input. Connect FB to the center tap of a resistive voltage-divider from the output (V
OUT
)
to SGND to set the output voltage. The FB voltage regulates to 1.245V (typ) when V
CNTRL
is above 1.5V (typ)
and to V
CNTRL
voltage when V
CNTRL
is below 1.245V (typ).
7 CNTRL
Control Input for Boost Converter Output-Voltage Programmability. Allows the feedback set-point voltage to be
set externally by CNTRL when V
CNTRL
is less than 1.245V. Pull CNTRL above 1.5V (typ) to use the internal
1.245V (typ) feedback set-point voltage.
8 ILIM 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.
10 MOUT Current-Monitor Output. MOUT sources a current 1/10th of I
APD
.
11 CLAMP Clamp Voltage Input. CLAMP is the external potential used for voltage clamping of MOUT.
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 (V
OUT
) 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 SHDN
Active-Low Shutdown Control Input. Apply a logic-low voltage to SHDN to shut down the device and reduce
the supply current to 2μA (max). Connect SHDN to IN for normal operation. Ensure that V
SHDN
is not greater
than the input voltage, V
IN
.
15 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.
16 LX
Drain of Internal 80V n-Channel DMOS. Connect inductor and diode to LX. Minimize the trace area at LX to
reduce switching noise emission.
—EP
Exposed Pad. Connect EP to a large contiguous copper plane at SGND potential to improve thermal
dissipation. Do not use as the main SGND connection.