Datasheet

LT3751
7
3751fc
Typical perForMance characTerisTics
RV
TRANS
(Pin 1/Pin 19): Transformer Supply Sense Pin.
Connect a resistor between the RV
TRANS
pin and the
V
TRANS
supply. Refer to Table 2 for proper sizing of the
RV
TRANS
resistor. The minimum operation voltage for
V
TRANS
is 4.75V.
UVLO1 (Pin 2/Pin 20): V
TRANS
Undervoltage Lockout Pin.
Senses when V
TRANS
drops below:
V
UVLO1
= 1.225+ 50µA • R
UVLO1
and trips the FAULT latch low, disabling switching. After
V
TRANS
rises above V
UVLO1
, toggling the CHARGE pin
reactivates switching.
OVLO1 (Pin 3/Pin 1): V
TRANS
Overvoltage Lockout Pin.
Senses when V
TRANS
rises above:
V
OVLO1
= 1.225+ 50µA • R
OVLO1
and trips the FAULT latch low, disabling switching. After
V
TRANS
drops below V
OVLO1
, toggling the CHARGE pin
reactivates switching.
UVLO2 (Pin 4/Pin 2): V
CC
Undervoltage Lockout Pin.
Senses when V
CC
drops below:
V
UVLO2
= 1.225+ 50µA • R
UVLO2
and trips the FAULT latch low, disabling switching. After
V
CC
rises above V
UVLO2
, toggling the CHARGE pin reac-
tivates switching.
OVLO2 (Pin 5/Pin 3): V
CC
Overvoltage Lockout Pin. Senses
when V
CC
rises above:
V
OVLO2
= 1.225+ 50µA • R
OVLO2
and trips the FAULT latch low, disabling switching. After
V
CC
drops below V
OVLO2
, toggling the CHARGE pin reac-
tivates switching.
FAULT (Pin 6/Pin 4): Open Collector Indication Pin. When
either V
TRANS
or V
CC
exceeds the user-selected voltage
range, or an internal UVLO condition occurs, a transistor
turns on. The part will stop switching. This pin needs a
proper pull-up resistor or current source.
HVGATE Pin Clamp Voltage
HVGATE Pin Clamp Voltage
–40
HVGATE PIN VOLTAGE (V)
11.0
10.9
10.8
10.7
10.5
10.6
10.4
40 600 80 100
3751 G19
12020
TEMPERATURE (°C)
–20
V
CC
= 24V
CLAMP = 0V
–40
HVGATE PIN VOLTAGE (V)
5.70
5.65
5.60
5.55
5.50
40 600 80 100
3751 G20
12020
TEMPERATURE (°C)
–20
V
CC
= 12V
CLAMP = 12V
pin FuncTions
DCM Trip Voltage (V
DRAIN
– V
TRANS
),
RV
TRANS
= RDCM = 25kΩ
–40
DCM TRIP VOLTAGE (V)
0.64
0.62
0.60
0.58
0.56
0.54
400 80
3751 G21
120
TEMPERATURE (°C)
V
TRANS
= 5V
V
TRANS
= 12V
V
TRANS
= 24V
V
TRANS
= 48V
(TSSOP/QFN)