lt4351 Linear Technology Corporation, lt4351 Datasheet - Page 5

• Manufacturer Part Number: lt4351
• Description: Mosfet Diode-or Controller
• Manufacturer: Linear Technology Corporation

Specifications are at T
TYPICAL PERFOR A CE CHARACTERISTICS
PI FU CTIO S
GATE (Pin 1): MOSFET Gate Drive Pin. This pin is tied to
the gate(s) of the external N-channel MOSFET(s). The
GATE pin drives high when UV is above the V
threshold, OV is below the V
greater than OUT by 15mV. When not driven high, GATE
actively pulls to GND. GATE can sink or source up to
600mA.
V
for the gate drive amplifier. It is either generated by the
onboard boost regulator or supplied externally. When
turning on the MOSFET(s), a large high current pulse flows
through this pin. Bypass the pin with a 1 F capacitor
placed in close proximity to the part. The voltage on this
pin is also the feedback for the boost regulator. If the V
voltage exceeds the V
is held off.
DD
U
(Pin 2): Gate Drive Supply Pin. This is the supply pin
U
5V/DIV
V
SW
A
Typical SW Pin Waveform
V
4.7 H INDUCTOR
U
IN
= 25 C unless otherwise specified.
IN
= 5V
voltage by 10.7V, the boost switch
W
OV(TH)
10 s/DIV
U
threshold and V
3451 G12
UV(TH)
IN
DD
is
V
the control circuitry and the boost regulator. It is also one
input in conjunction with OUT for controlling the
MOSFET(s). Bypassing should include a low ESR/ESL
capacitor placed in close proximity to the part.
SW (Pin 4): Boost Regulator Switch Pin. This pin is the
boost regulator switch output. It is connected to the boost
inductor and the boost diode. Peak switch current is
limited internally to 450mA. If an external V
used, leave this pin open.
GND (Pin 5): Device Ground Pin. This pin is ground for the
boost switch, gate driver as well as the control circuitry.
Tie the V
close to this pin to minimize the effects of switching
currents on part performance.
IN
(Pin 3): Input Supply Pin. This pin is the supply pin for
5V/DIV
V
IN
SW
and V
SW Pin Waveform at Maximum
Boost Regulator Output
V
4.7 H INDUCTOR
IN
= 5V
DD
bypass capacitors and ground plane
10 s/DIV
3451 G13
LT4351
DD
supply is
sn4351 4351fs
5