www.fairchildsemi.com
ILC6376/77
0.5A, 300kHz, SO-8 PWM/PFM Step Down Converter with
Shutdown
Features
±2.5% accurate output voltages
Guaranteed 500mA output current
95% efficiency
55µA no load battery input current (ILC6377)
1.5µA shutdown current
Built in short circuit and overcurrent protection
Undervoltage lockout and soft-start
External transistor drive available for higher I
OUT
300kHz operation
Automatic switchover to PFM mode at low currents for
longest battery life (ILC6377)
• Fixed 3.3V or 5V or adjustable output
• SO-8 package
•
•
•
•
•
•
•
•
•
•
Description
T
he ILC6376/77 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 ILC6376/77 uses a unique p-channel architecture with
built-in charge pump to maintain low on-resistance, even at
low input voltages. The ILC6376 operates in PWM mode
with 300kHz switching frequency. The ILC6377 does the
same at high and medium load currents. When the load
current drops and the device hits approximately 25% duty
cycle, ILC6377 automatically switches over to PFM or pulse
skipping mode. PFM (pulse frequency modulation) 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 ILC6376/77 consumes only 1.5µA current.
The ILC6376/77SOXX offers fixed 3.3V or 5V output while
ILC6376/77SOADJ allows adjustable output. Both versions
of ILC6376/77 are available in an SO-8 surface mount
package.
Applications
•
•
•
•
Cellular Phones
Palmtops and PDAs
Portable Instrumentation
Buck Converter for Industrial / Networking Applications
Typical Applications
SD1
V
IN
*C
IN
1
+
2
3
4
8
S/D
10µF
ILC6376/77
(TOP VIEW)
7
6
5
+
L
22µH
V
OUT
C
L
47µF
C
SS
Fig 1. Typical step-down DC-DC
converter application
SD1: SS12 Schottky Diode (FAIRCHILD)
C
L
: 10V/47µF Tantalum Capacitor (NICHICON, F93)
C
SS
: 4700pF Ceramic Capacitor
C
IN
: 16V / 10µF Tantalum Capacitor (NICHICON, F93)
Rev. 1.5 November 2001
©2001 Fairchild Semiconductor Corporation
ILC6376/77
Absolute Maximum Ratings
(T
A
=25°C)
Parameter
V
IN
Input Voltage Pin
V
OUT
Pin (ILC6376/77SOXX)
FB Pin (ILC6376/77SOADJ)
Voltage on L
X
pin
Peak Switch Current on L
X
pin
Voltage on P_BST pin
Current EXT1, EXT2 pins
Voltage on all other pins
Continuous Total Power Dissipation
Operating Ambient Temperature
Storage Temperature
Symbol
V
IN
V
OUT
V
FB
V
LX
I
LX
V
DP
_BST
I
EXT
1, I
EXT
2
~
P
D
T
OPR
T
STG
Ratings
-0.3 to +12
-0.3 to +12
-0.3 to V
IN
+0.3
V
IN
- V
LX
= -0.3 to +12
700
V
IN
- V
P
_BST = -0.3 to +12
±50
-0.3 to V
IN
+ 0.3
300
-30~+80
-40~+125
Units
V
V
V
mA
V
mA
V
mW
°C
°C
Electrical Characteristics ILC6376/77SO33
V
OUT
= 3.3V, V
IN
= 4V, F
OSC
=300kHz, I
OUT
= 130mA, T
A
= 25°C, unless otherwise specified. Circuit configuration figure 1.
Parameter
Output Voltage
Input Voltage
Output Maximum Current
Input Current Supply
Shutdown Current
L
X
Switch On - Resistance
L
X
Switch Leakage Current
Oscillator Frequency
Max Duty Cycle
PFM Duty Cycle
Efficiency
Undervoltage Lockout
Soft-Start Time
Shutdown Input Voltage
EXT1, EXT2 Hi On-
Resistance
EXT1, EXT2 Low On-
Resistance
Symbol
V
OUT
V
IN
I
OUT(MAX)
I
IN
I
S/D
R
ds(on)
I
LXL
F
OSC
MAXDTY
PFMDTY
EFFI
V
UVLO
T
SS
V
SD
REXt
HI
REXt
LOW
Conditions
Min.
3.218
500
V
IN
3.5V, No Loads
ILC6376
ILC6377
Typ.
3.300
600
1480
50
1.5
0.64
Max.
3.383
10
2190
86
2.5
0.85
2.0
255
300
100
25
95
345
Units
V
V
mA
µA
µA
Ω
µA
kHz
%
%
%
V
msec
V
Ω
Ω
V
S/D
= 0V
Open Loop Measurement, V
S/D
=
V
IN
, V
LX
= V
IN
- 0.2V, V
OUT
= 3V
Open Loop Measurement, V
OUT
=
V
IN
, V
LX
= 0V
Measurement Waveform at EXT pin
V
IN
= 3.6V I
OUT
= 20mA
No Load (ILC6377)
Minimum V
IN
when V
ref
does not
start up
V
REF
rises to 0V from 0.9V
High = Regulator “ON”
Low = Regulator “OFF”
3V applied to V
OUT
with no external
components
3.6V applied to V
OUT
with no
external components
15
0.9
6.0
0.65
35
1.8
10.0
16.0
0.2
47
37
35
29
©2001 Fairchild Semiconductor Corporation
3
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