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© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1631
January 29, 1998
FEATURES
• High efficiency 90%
• Power-saving shutdown mode (7µA typical)
• Internal 2A switch
• 120kHz switching rate
• Adjustable switch current limit
• On-chip low battery detector
DESCRIPTION
The SC1631 is a high efficiency step up DC-DC
converter. Only four external components are required
to deliver a fixed voltage of 3V, 3.3V, or 5V. Efficiency
beyond 87% can be easily achieved at 100mA load
with 2.2V to 3V input voltages.
A logic-controlled shutdown mode is provided for
power saving. Switch current limit can be programmed
with a resistor. The low battery detector can be
configured as a linear regulator or a burst mode
controller providing extremely low supply current
operation.
A switching rate of 120kHz reduces the inductor size inductors of 25µH to 50µH are recommended for most
applications.
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
APPLICATIONS
• Palmtop and notebook computers
• Pocket organizers
• Cameras
• Pagers
• Battery backup supplies
• Portable instruments
ABSOLUTE MAXIMUM RATINGS
Parameter Symbol Maximum Units
Supply Voltage V
IN
7.0 V
Operating
Temperature Range
T
A
0 to 70 °C
Storage Temperature
Range
T
STG
-65 to 125 °C
BLOCK DIAGRAM
Note:
(1) Add suffix ‘TR’ for tape and reel.
ORDERING INFORMATION
DEVICE
(1)
OUTPUT VOLTAGE PACKAGE
SC1631CS
SC1631-3CS
SC1631-5CS
3.3V
3.0V
5.0V
SO-8
PIN CONFIGURATION
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© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1631
January 29, 1998
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, TA = 25°C, VIN = 3.0V
Test Conditions Test Limits
Parameter V
IN
I
L
Min Typ Max Units
Input Voltage 1.5 7.0 V
Output Voltage
SC1631
SC1631-3
SC1631-5
I
L
= 200mA
3.16
2.88
4.80
3.30
3.00
5.00
3.44
3.12
5.20
V
Switch Off Current 105 140 µA
No Load Current
SC1631/SC1631-3
SC1631-5
160
180
µA
Shutdown Mode Current 7 15 µA
Recovery Time from Shutdown V
IN
=2.5V IL=200mA 0.4 ms
Efficiency
SC1631/SC1631-3
SC1631-5
I
L
=200mA 87
90
%
Line Regulation
SC1631
SC1631-3
SC1631-5
V
IN
=1.8 - 3.3V
V
IN
=1.8 - 3.0V
V
IN
=2.2 - 3.3V
I
L
=100mA 0.6
0.5
0.8
%V
OUT
Load Regulation
SC1631/SC1631-3
SC1631-5
I
L
=10mA - 300mA 0.3
0.8
%V
OUT
Oscillator Frequency 90 120 150 kHz
LBI Pin Trip Point 1.17 1.22 1.27 V
LBO “On Resistance” V
IN
= 2V 45
Ω
SW “On Resistance”
SC1631/SC1631-3
SC1631-5
0.5
0.4
Ω
SW Off Leakage 1µA
Input Pin Bias Current 10 nA/Pin
Output Pin Leakage 10 nA/Pin
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© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1631
January 29, 1998
TYPICAL PERFORMANCE CHARACTERISTICS
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© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1631
January 29, 1998
TYPICAL PERFORMANCE CHARACTERISTICS (cont.)
TYPICAL APPLICATION CIRCUIT
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© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1631
January 29, 1998
Figure 3. 1-Cell Input 3V Output Step-Up Converter
Figure 2. 5V Output Step-Up Converter
APPLICATION EXAMPLES
Figure 1. 3V Output Step-Up Converter
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© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1631
January 29, 1998
APPLICATION EXAMPLES (cont.)
Figure 6. Low Supply Current Burst Mode Step-Up Converter
Figure 5. 4-Cell Input Step-Up/Step-Down Converter
Figure 4. 1-Cell Input 5V Output Step-Up Converter
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© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1631
January 29, 1998
DEVICE OUTLINE - SO-8
PIN DESCRIPTIONS
PIN 1: I
LIM
/SD (1) Connected to VIN pin through a re-
sistor to set the switch peak current. It
serves to protect the IC and inductor,
as well as to improve efficiency and
output ripple. However, the supply capability of the SC1631 is limited by the
current limit resistor (see typical performance characteristics). The I
LIM
/SD
pin should be shorted to V
IN
if limiting
switch peak current is not required.
(2) The SC1631 goes into shutdown
mode and consumes less than 10µA
when the I
LIM
/SD pin is pulled to
ground.
PIN 2: V
IN
Input supply.
PIN 3: SW Drain of the power switch, to be con-
nected to the inductor and diode.
PIN 4: SGND Ground connected to the source of the
power switch.
PIN 5: CGND Ground for control circuits of the IC. It
should be separated from SGND to
avoid interference.
PIN 6: LBO Open drain output of the battery low
detector, with 45 Ohm “On Resistance” at V
IN
=2V. It is pulled low when
the voltage on the LBI pin is below
1.22 volts.
PIN 7: LBI The inverting input of the battery low
detector, of which the non-inverting
input is internally connected to the
1.22V voltage reference.
PIN 8: V
OUT
The output voltage feeds back to the
IC through this pin.
PIN CONFIGURATION
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