ltc3872ets8-trpbf Linear Technology Corporation, ltc3872ets8-trpbf Datasheet - Page 5

• Manufacturer Part Number: ltc3872ets8-trpbf
• Description: No Rsense Current Mode Boost Dc/dc Controller
• Manufacturer: Linear Technology Corporation

PI FU CTIO S
IPRG (Pin 1/Pin 4): Current Sense Limit Select Pin.
I
pensation point. Nominal voltage range for this pin is
0.7V to 1.9V.
V
external resistor divider across the output.
GND (Pin 4/Pin 1): Ground Pin.
NGATE (Pin 5/Pin 8): Gate Drive for the External N-Channel
MOSFET. This pin swings from 0V to V
V
decoupled to GND (Pin 4).
FUNCTIONAL DIAGRAM
TH
FB
IN
U
(Pin 2/Pin 3): It serves as the error amplifi er com-
(Pin 3/Pin 2): Receives the feedback voltage from an
(Pin 6/Pin 7): Supply Pin. This pin must be closely
V
RUN/SS
IN
U
0.7μA
UNDERVOLTAGE
COMPARATOR
SHUTDOWN
LOCKOUT
U
SHDN
SOFT-START
UV
INTERNAL
(TS8/DD8)
RAMP
REFERENCE
VOLTAGE
IN
.
I
TH
1.2V
AMPLIFIER
ERROR
+
–
CURRENT LIMIT
BUFFER
I
TH
CLAMP
RUN/SS (Pin 7/Pin 6): Shutdown and external soft-start
pin. In shutdown, all functions are disabled and the NGATE
pin is held low.
SW (Pin 8/Pin 5): Switch node connection to inductor and
current sense input pin through external slope compensa-
tion resistor. Normally, the external N-channel MOSFET’s
drain is connected to this pin.
Exposed Pad (NA/Pin 9): Ground. Must be soldered to PCB
for electrical contact and rated thermal performance.
–
+
1.2V
GND
LATCH
RS
–
LOGIC CIRCUIT
SWITCHING
R
I
LIM
Q
+
S
SW
COMPARATOR
CURRENT
V
COMPENSATION
IN
OSCILLATOR
550kHz
SLOPE
LTC3872
NGATE
IPRG
V
3872 FD
FB
3872fa
5