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
P WM /PFM
P rotection
L
X
GND
EXT1
RAMP WAVE
V
I N
V
O UT
P_BST
GATE
DRIV ER
GENERATOR,
OSCILLATOR
CONTROLLER
+
-
PWM
Comp
EXT2
+
-
Error
Amp
1
5
4
6
3
2
7
8
S/ D,
So ftstar t,
Vref
S /D,
V ref
with
S oft-
start
ILC6377
(TOP VIE W)
3
4
5
1
2
6
7
8
L
X
FB
EXT1
S/D,
GND
P_BST
EXT2
V
I N
ILC6377SO-Adj
C
SS
SO-8 Package
ILC6377
(TOP VIE W)
3
L
X
V
O UT
EXT1
4
5
S/D,
GND
1
2
6
7
8
P_BST
EXT2
V
I N
C
SS
SO-8 Package
ILC6377SO-XX
Ordering Information
ILC6377SO-33
3.3V, 300 kHz step-down PWM/PFM converter
ILC6377SO-50
5V, 300 kHz step-down PWM/PFM converter
ILC6377SO-Adj
Adjustable, 300 kHz step-down PWM/PFM converter
Pin
Symbol
Function
1
V
IN
Power Supply
2
EXT2
External gate drive pin (low when
P-Ch FET is ON)
3
P-BST
P-Ch gate boost
4
S/D
Softstart, V
ref
Shutdown, also soft-start capacitor
pin and V
ref
output
5
V
OUT
/FB
Output voltage sense pin for
ILC6377SO-XX; 1V feedback for
ILC6377SO adj
6
GND
Ground connection
7
EXT1
External gate drive pin (low when
P-Ch FET is on)
8
L
X
Inductor switch pin
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
0.5A, 300kHz, SO-8 PWM/PFM Step Down Converter with Shutdown
Impala Linear Corporation
2
(408) 574-3939
www.impalalinear.com
June 1999
ILC6377 1.3
Conditions
V
IN
3.5V, No Loads
V
S/D
= 0V
Open Loop Measurement, V
S/D
= V
IN
, V
LX
=
V
IN
- 0.4V, 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
Minimum V
IN
when V
ref
does not start up
V
ref
rises to 0V from 0.9V
Parameter
Output Voltage
Input Voltage
Output Voltage
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
Symbol
V
OUT
V
IN
I
OUT
I
IN
I
S/D
R
ds(on)
I
LXL
F
OSC
MAXDTY
PFMDTY
EFFI
V
UVLO
T
SS
Unless Otherwise specified all limits are at V
OUT
= 3.3V, V
IN
= 4V, F
OSC
=300kHz, I
OUT
= 130mA,T
A
= 25C. Circuit configuration of figure 1.
Parameter
V
IN
Input Voltage Pin
V
OUT
Pin (ILC6370SO-XX)
FB Pin (ILC6377SO-Adj)
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
EXT1,
I
EXT2
~
P
D
T
OPR
T
STG
Ratings
-0.3 to +12
-0.3 to +12
-0.3 to V
IN
+12
V
IN
- V
LX
= 0.3 to +12
700
V
IN
- V
P
_BST = 0.3 to +12
50
-0.3 to V
IN
500
-30~+80
-40~+125
Units
V
V
V
mA
V
mA
V
mA
C
C
Typ
3.300
600
55
1.5
0.64
300
100
17
95
10.0
Min
3.218
500
255
10
1
6.0
Max
3.383
10
86
2.5
0.85
2.0
345
25
1.8
16.0
Units
V
V
mA
A
A
A
kHz
%
%
%
V
msec
Absolute Maximum Ratings (T
A
=25C)
Electrical Characteristics ILC6377SO-33
0.5A, 300kHz, SO-8 PWM/PFM Step Down Converter with Shutdown
Impala Linear Corporation
3
(408) 574-3939
www.impalalinear.com
June 1999
ILC6377 1.3
Min
4.875
500
255
10
1
6.0
3.0
0.65
Typ
5.000
600
71
1.5
0.44
300
100
17
95
10.0
5.0
24
20
Symbol
V
OUT
V
IN
I
OUT
I
IN
I
S/D
R
ds(on)
I
LXL
F
OSC
MAXDTY
PFMDTY
EFFI
V
UVLO
T
SS
T
PRO
V
S/D
REXt
HI
REXt
LOW
Parameter
Output Voltage
Input Voltage
Output Current
Input Supply Current
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
Internal Protection Time
Shutdown Input Voltage
EXT1, EXT2 Hi On-Resistance
EXT1, EXT2 Low On-Resistance
Parameter
Internal Protection Time
Shutdown Input Voltage
EXT1, EXT2 Hi On-Resistance
EXT1, EXT2 Low On-Resistance
Symbol
T
PRO
V
SD
REXt
HI
REXt
LOW
Conditions
Time from V
OUT
= 0V to V
S/D
going low
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
Min
3.0
0.65
Typ
5.0
3.5
29
Max
8.0
0.2
47
37
Units
Msec
V
Conditions
V
IN
5.25V, No Load
V
S/D
= 0V
Open Loop Measurement, V
S/D
= V
IN
,
V
LX =
V
IN
- 0.4V, V
OUT
= 4.5V
Open Loop Measurement, V
OUT
= V
IN
,
V
LX
= 0V
Measure Waveform at EXT pin V
IN
= 5.3V
I
OUT
= 20mA
No Load
Minimum V
IN
when V
ref
does not start up
V
ref
rises to 0V from 0.9V
Time form V
OUT
m = 0V to V
S/D
going low
High = Regulator "ON"
Low = Regulator "OFF"
Open Loop Measurement
Open Loop Measurement
Max
5.125
10
110
2.5
0.58
2.0
345
25
1.8
16.0
8.0
0.2
32
26
Units
V
V
mA
A
A
A
kHz
%
%
%
V
msec
msec
V
Electrical Characteristics ILC6377SO-33
Electrical Characteristics ILC6377SO-50
Unless Otherwise specified all limits are at V
OUT
= 3.3V, V
IN
= 4V, F
OSC
=300kHz, I
OUT
= 130mA,T
A
= 25C. Circuit configuration of figure 1.
Unless Otherwise specified all limits are at V
OUT
= 5.0V, V
IN
= 6V, F
OSC
=300kHz, I
OUT
= 200mA, T
A
= 25C. Circuit configuration of figure 1.
0.5A, 300kHz, SO-8 PWM/PFM Step Down Converter with Shutdown
Impala Linear Corporation
4
(408) 574-3939
www.impalalinear.com
June 1999
ILC6377 1.3
Parameter
Symbol
Conditions Min
Typ
Max
Units
Feedback Voltage (pin5)
V
FB
.995 1.000
1.015
V
Input Voltage
V
OUT
R
FB1
+ R
FB2
< 2M
3
8
V
Output Current
I
OUT
500
600
mA
Input Supply Current
I
IN
V
IN
5.25V, No Load
71
110
A
Shutdown Current
I
S/D
V
S/D
= 0V
1.5
2.5
A
L
X
Switch On-Resistance
R
ds(on)
Open Loop Measurement, V
S/D
= V
IN
, 0.44
0.58
V
LX
= V
IN
- 0.4V, V
OUT
= 4.5V
L
X
Switch On-Resistance
I
LXL
Open Loop Measurement, V
OUT
= V
IN
, 2.0
A
V
LX
= 0V
Shutdown Input Voltage
V
S/D
High = Regulator "ON"
0.65
0.2
V
Low = Regulator "OFF"
Oscillator Frequency
F
OSC
Measure Waveform at EXT pin V
IN
=
255
300
345
kHz
5.3V I
OUT
= 20mA
Max Duty Cycle
MAXDTY
100
%
PFM Duty Cycle
PFMDTY
No Load
10
17
25
%
Efficiency
EFFI
95
%
Undervoltage Lockout
V
UVLO
Minimum V
IN
when V
ref
does not start up
1
1.8
V
Soft-Start Time
T
SS
V
ref
rises to 0V from 0.9V
6.0
10.0
16.0
msec
Internal Protection Time
T
PRO
Time from V
OUT
m = 0V to V
S/D
going low
3.0
5.0
8.0
msec
EXT1, EXT2 Hi On-Resistance
REXt
HI
Open Loop Measurement
24
32
EXT1, EXT2 Low On-Resistance
REXt
LOW
Open Loop Measurement
20
26
Electrical Characteristics ILC6377SO-Adj
Unless Otherwise specified all limits are at V
OUT
programmed to 5.0V, V
IN
= 6V, F
OSC
=300kHz, I
OUT
= 200mA, T
A
= 25C. Circuit configuration of figure 1.
0.5A, 300kHz, SO-8 PWM/PFM Step Down Converter with Shutdown
Impala Linear Corporation
5
(408) 574-3939
www.impalalinear.com
June 1999
ILC6377 1.3
+
V
O UT
ILC6377
(TOP VIE W)
3
4
5
1
2
6
7
8
+
C
L
V
I N
S/D
C
SS
SD1
L
*C
I N
Fig 1. Typical step-down DC-DC
converter application
SD1 : MA735 Schottky Diode ( MATSUSHITA )
C
L
: 10V/47
F Tantalum Capacitor ( NICHICON, F93 )
C
SS
: 4700pF Ceramic Capacitor
C
IN
: 16V / 10
F Tantalum Capacitor ( NICHICON, F93 )
22
H
47
F
10
F
External component selection
Proper selection of external components is important for
achieving high performance. The output inductor selected
should have low DC resistance on the order of 0.2W or less
and saturation current rating of 1A or higher.
Recommended inductors are Sumida CD54 (22mH, 0.18W
max DC resistance) or Coilcraft DO3308P-223 (22mH,
0.18W max DC resistance) or equivalent.
The catch diode should be a schottky diode with low for-
ward drop and rated at 1A or greater current, MA735 or it's
equivalent is recommended.
Input and output capacitors should be tantalum capacitors
with low equivalent series resistance (ESR) and voltage rat-
ing higher than the actual application.
Soft-start
Pin 4 of ILC6377 functions as the soft-start pin as well as the
shutdown pin. A soft-start capacitor (from pin 4 to ground)
controls the rate at which the power supply starts up; thus
preventing large overshoots at the output as well as large in-
rush current. The value for CSS should be 100pF or greater.
Shutdown
The ILC6377 is placed in shutdown mode by taking pin 4 to
ground. In shutdown, the quiescent current of the device is
under 2mA. When using the shutdown feature, pin 4 must
be driven from an open collector or open drain output with-
out employing an external pull-up resistor, as shown in fig-
ure 2. Since pin 4 is also used to charge an external capac-
itor for soft-start, this pin should not be driven from a push-
pull CMOS type output.
Over-current and short-circuit protection
In the event of an over-current or short-circuit condition, the
ILC6377 cycles the soft-start pin in a hiccup mode to provide
fault protection. When the output voltage decreases due to
overload, the ILC6377 will operate continuously at the max-
imum duty cycle. If the period of maximum duty cycle oper-
ation exceeds TPRO (typically 5 msec), pin 4 will be pulled
low; thus discharging the external soft-start capacitor CSS.
This action inhibits the regulator's PWM action. Next, the
ILC6377's soft-start circuitry starts recharging CSS and initi-
ates a controlled start-up. If the overload condition continues
to exist, the above sequence of events will repeat; thus con-
tinuing to cycle the soft-start function.
Note that very little power is dissipated with this method of
fault protection versus constant current limit protection.
Even though the internal power MOSFET is pulsed on and
off at high peak current, the DC current is low; thus leading
to low power dissipation even under short-circuit conditions.
Keep in mind that the duration of maximum duty cycle
condition is used to trigger the
I
LC6377's fault protec-
tion circuit. As such, a small input-output (V
IN
- V
OUT
)
differential voltage may trigger the device's fault protec-
tion circuitry even at low output current.
Undervoltage Lockout
The undervoltage lockout feature prevents faulty operation
by disabling the operation of the regulator when input volt-
age is below the minimum operating voltage, VUVLO. When
the input voltage is lower than VUVLO the device disables
the internal P-channel MOSFET and provides "high" output
at both EXT1 and EXT2 outputs.
Figure 2 shows a typical fixed output voltage step-down DC-DC
converter application circuit for ILC6377SO-XX
Fig. 1: Typical step-down wn DC-DC
converter application
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