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Impala Linear Corporation
1
(408) 574-3939
www.impalalinear.com
June 1999
ILC6377 1.3
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.
!
±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
!
Fixed 3.3V or 5V or adjustable output
!
SO-8 package
!
Cellular Phones
!
Palmtops and PDAs
!
Portable Instrumentation
!
Buck Converter for Industrial / Networking Applications
PWM/PFM
CONTROLLER
Protection
L
X
GND
EXT1
RAMP WAVE
GENERATOR,
V
IN
V
O UT
P_BST
GATE
DRIVER
+
PWM
Comp
-
EXT2
+
Amp
-
1
5
4
6
3
2
7
8
S/D,
Softstar t,
Vref
S/D,
with
start
ILC6377
(TOP VIEW)
3
4
5
1
2
6
7
8
L
X
EXT1
FB
S/D,
C
SS
GND
P_BST
EXT2
V
IN
ILC6377SO-Adj
SO-8 Package
ILC6377
(TOP VIEW)
3
L
X
EXT1
GND
V
O UT
4
5
S/D,
C
SS
1
2
6
7
8
P_BST
EXT2
V
IN
SO-8 Package
ILC6377SO-XX
Ordering Information
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
ILC6377SO-33
ILC6377SO-50
ILC6377SO-Adj
Pin
1
2
Symbol
V
IN
EXT2
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
3
4
P-BST
S/D
Softstart, V
ref
V
OUT
/FB
5
6
7
GND
EXT1
8
L
X
ILC6377
0.5A, 300kHz, SO-8 PWM/PFM Step Down
Converter with Shutdown
Impala Linear Corporation
General Description
Features
Applications
Block Diagram
Pin Package Configurations
Pin Description