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LTC3670_15 Datasheet, PDF (6/12 Pages) Linear Technology – Monolithic 400mA Buck Regulator with Dual 150mA
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LTC3670
PIN FUNCTIONS
SW (Pin 1): Buck Regulator Switch Node Connection to In-
ductor. This pin connects to the drains of the buck regulator’s
main PMOS and synchronous NMOS switches.
GND (Pin 2): Ground.
ENLDO1 (Pin 3): Enables the First Low Dropout Linear
Regulator (LDO1) When High. This is a MOS gate input.
There is an internal 4MΩ pull-down.
ENLDO2 (Pin 4): Enables the Second Low Dropout Linear
Regulator (LDO2) When High. This is a MOS gate input.
There is an internal 4MΩ pull-down.
ENBUCK (Pin 5): Enables the Buck Converter When High.
This is a MOS gate input. There is an internal 4MΩ pull-
down.
BUCKFB (Pin 6): Feedback Voltage Input for the Buck
Regulator. Typically, an external resistor divider feeds a
fraction of the buck output voltage to this pin.
PGOOD (Pin 7): Power Good Open-Drain NMOS Output.
The PGOOD pin goes Hi-Z when all enabled outputs are
within 8% of final value.
LDO2_FB (Pin 8): Feedback Voltage Input for the Second
Low Dropout Linear Regulator (LDO2). Typically, an ex-
ternal resistor divider feeds a fraction of the LDO2 output
voltage to this pin.
LDO1_FB (Pin 9): Feedback Voltage Input for the First Low
Dropout Linear Regulator (LDO1). Typically, an external
resistor divider feeds a fraction of the LDO1 output volt-
age to this pin.
LDO1 (Pin 10): Output of the First Low Dropout Linear
Regulator. This pin must be bypassed to ground with a
1μF or greater ceramic capacitor.
LDO2 (Pin 11): Output of the Second Low Dropout Linear
Regulator. This pin must be bypassed to ground with a
1μF or greater ceramic capacitor.
VIN (Pin 12): Input Supply. This pin should be bypassed
to ground with a 2.2μF or greater ceramic capacitor.
Exposed Pad (Pin 13): Ground. This pin must be soldered
to the PCB.
BLOCK DIAGRAM
VIN
12
SW 1
GND 2
BUCKFB 6
400mA BUCK
ENABLE
BUCK
2.25MHz
OSC
ENLDO1 3
ENLDO2 4
ENBUCK 5
800mV
REFERENCE
LOGIC
POWER GOOD
COMPARATORS
ENABLE_LDO2
ENABLE_LDO1
LDO2
6
LDO1
GND
13
10 LDO1
11 LDO2
7 PGOOD
9 LDO1_FB
8 LDO2_FB
3670 BD
3670f
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