LTC3803-5 Linear Technology, LTC3803-5 Datasheet - Page 6

• Manufacturer Part Number: LTC3803-5
• Description: Constant Frequency Current Mode Flyback DC/DC Controller
• Manufacturer: Linear Technology

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PI FU CTIO S
I
serves as the error amplifier compensation point as well as
the run/shutdown control input. Nominal voltage range is
0.7V to 1.9V. Forcing this pin below 0.28V causes the
LTC3803-5 to shut down. In shutdown mode, the NGATE
pin is held low.
GND (Pin 2): Ground Pin.
V
nal resistive divider across the output.
LTC3803-5
BLOCK DIAGRA
6
TH
FB
/RUN (Pin 1): This pin performs two functions. It
U
(Pin 3): Receives the feedback voltage from an exter-
3
2
V
GND
FB
U
REFERENCE
800mV
U
REGULATOR
+
–
SHUNT
CLAMP
START
W
SOFT-
V
CC
ERROR
AMPLIFIER
1.2V
5
V
CC
1
I
0.3µA
TH
/RUN
0.28V
20mV
+
–
–
+
SENSE (Pin 4): This pin performs two functions. It moni-
tors switch current by reading the voltage across an
external current sense resistor to ground. It also injects a
current ramp that develops slope compensation voltage
across an optional external programming resistor.
V
(Pin 2).
NGATE (Pin 6): Gate Drive for the External N-Channel
MOSFET. This pin swings from 0V to V
CC
SHUTDOWN
COMPARATOR
CURRENT
COMPARATOR
OSCILLATOR
(Pin 5): Supply Pin. Must be closely decoupled to GND
200kHz
R
S
Q
SWITCHING
LOGIC AND
BLANKING
CIRCUIT
CURRENT
SLOPE
SHUTDOWN
COMP
RAMP
V
CC
< V
TURNON
V
CC
UNDERVOLTAGE
GATE
DRIVER NGATE
CC
LOCKOUT
.
SENSE
38035 BD
6
4
38035f