Impala Linear Corporation
ILC6377
0.5A, 300kHz, SO-8 PWM/PFM Step Down
Converter with Shutdown
General Description
The ILC6377 is a 95% efficient, 300kHz step-down DC-DC
converter in an SO-8 package; capable of delivering 500mA
output current. The device is also capable of driving an
external FET for higher output current applications.
The ILC6377 uses a unique p-channel architecture with
built-in charge pump to maintain low on-resistance, even at
low input voltages. At high or normal currents the ILC6377
operates in PWM mode with 300kHz operating frequency.
When the load current drops and the device hits approxi-
mately 17% duty cycle, it automatically switches over to
PFM or pulse skipping mode. PFM (pulse frequency mod-
ulation) mode of operation extends efficiency at light loads.
Start-up is controlled via an external soft-start capacitor. The
device will automatically re-enter start-up mode when an
output current overload condition is sensed; thus providing
automatic short-circuit protection. Voltage lockout prevents
faulty operation below the minimum operating voltage level.
In shutdown, the ILC6377 consumes only 1.5mA current.
The ILC6377SO-XX offers fixed 3.3V or 5V ouput while
ILC6377SO-Adj allows adjustable output. Both versions of
ILC6377 are available in an SO-8 surface mount package.
Features
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鹵2.5% accurate output voltages
Guaranteed 500mA output current
95% efficiency
55mA no load battery input current
1.5mA shutdown current
Built in short circuit and overcurrent protection
Undervoltage lockout and soft-start
External transistor drive available for higher Iout
300kHz operation
Automatic switchover to PFM mode at low
currents for longest battery life
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Fixed 3.3V or 5V or adjustable output
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SO-8 package
Applications
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Cellular Phones
Palmtops and PDAs
Portable Instrumentation
Buck Converter for Industrial / Networking Applications
Block Diagram
V
I N
V
O UT
1
5
8 L
X
Ordering Information
ILC6377SO-33
ILC6377SO-50
ILC6377SO-Adj
3.3V, 300 kHz step-down PWM/PFM converter
5V, 300 kHz step-down PWM/PFM converter
Adjustable, 300 kHz step-down PWM/PFM converter
+
Error
Amp
-
S/ D, 4
So ftstar t,
Vref
S /D,
V ref
with
S oft-
start
P rotection
7 EXT1
+
PWM
Comp
-
GATE
DRIV ER
2 EXT2
3 P_BST
Pin Description
Pin
Symbol
V
IN
EXT2
P-BST
S/D
Softstart, V
ref
V
OUT
/FB
P WM /PFM
CONTROLLER
RAMP WAVE
GENERATOR,
OSCILLATOR
Function
Power Supply
External gate drive pin (low when
P-Ch FET is ON)
P-Ch gate boost
Shutdown, also soft-start capacitor
pin and V
ref
output
Output voltage sense pin for
ILC6377SO-XX; 1V feedback for
ILC6377SO adj
Ground connection
External gate drive pin (low when
P-Ch FET is on)
Inductor switch pin
6 GND
1
2
3
4
Pin Package Configurations
V
I N
EXT2
P_BST
1
2
3
8
L
X
EXT1
GND
V
O UT
V
I N
EXT2
P_BST
1
2
3
8
L
X
EXT1
GND
FB
5
ILC6377
(TOP VIE W)
7
6
5
ILC6377
(TOP VIE W)
7
6
5
S/D,
4
C
SS
S/D,
4
C
SS
6
7
8
GND
EXT1
L
X
ILC6377SO-XX
SO-8 Package
ILC6377SO-Adj
SO-8 Package
Impala Linear Corporation
ILC6377 1.3
(408) 574-3939
www.impalalinear.com
June 1999
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