lt3571 Linear Technology Corporation, lt3571 Datasheet - Page 6

• Manufacturer Part Number: lt3571
• Description: 75v Dc/dc Converter For Apd Bias
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
LT3571
NC (Pin 1): No Connect.
APD (Pin 2): APD Cathode Pin. Connect APD cathode to
this pin.
MONIN (Pin 3): Current Monitor Power Supply Pin. An
external lowpass fi lter can be included here to further
reduce supply voltage ripple. This pin also serves as the
inverting input of the current sense amplifi er. Put a sense
resistor between the MONIN pin and the V
the boost converter output current limit as 200mV/R
Connect the MONIN pin directly to the V
output current limit function is not used.
V
this pin and GND plane. Minimize the length of the trace
to the capacitor. Also serves as the noninverting input of
the current sense amplifi er.
SW (Pin 5, 6): Switch Pin. Minimize the trace length on
this pin to reduce EMI.
GND (Pin 7, 10): Ground. Pins connected internally. For
best performance, connect both pins to board ground.
SYNC (Pin 8): Frequency Synchronization Pin. Connect an
external clock signal here. R
to program a switching frequency 20% slower than the
SYNC pulse frequency. Synchronization (switch turn-on)
occurs a fi xed delay after the rising edge of SYNC. Tie the
SYNC pin to ground if this feature is not used.
6
OUT
(Pin 4): Boost Output Pin. Put a capacitor between
T
resistor should be chosen
OUT
OUT
pin to set
pin if the
SENSE
.
R
quency using a resistor to GND (see Typical Performance
Characteristics for values). For SYNC function, choose
the resistor to program a frequency 20% slower than the
SYNC pulse frequency. Do not leave this pin open.
V
bypassed.
SHDN (Pin 12): Shutdown Pin. Tie to 1.5V or higher to
enable device; 0.4V or less to disable device. Also functions
as soft-start. Use RC fi lter as shown in Figure 1.
V
up to 100μA. Do not over drive this pin. Bypass with a
10nF or larger capacitor.
CTRL (Pin 14): Internal Reference Override Pin. The CTRL
pin allows the FB voltage to be externally adjusted between
0V and 1V to adjust the output voltage. Tie this pin higher
than 1.2V to use the internal reference of 1V.
FB (Pin 15): Feedback Pin. Connect to output resistor
divider tap.
MON (Pin 16): Current Monitor Output Pin. Sources a
current equal to 20% of the APD current and converts to
a reference voltage through an external resistor.
Exposed Pad (Pin 17): Ground. The Exposed Pad must
be soldered to the PCB.
T
IN
REF
(Pin 9): Switching Frequency Pin. Set switching fre-
(Pin 11): Input Supply Pin. This pin must be locally
(Pin 13): Reference Output Pin. This pin can supply
3571f