© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1633
January 29, 1998
Note:
(1) Add suffix ‘TR’ for tape and reel.
FEATURES
• High efficiency 87%
• Power-saving shutdown mode (7µA typical)
• Internal 0.8A switch
• 120kHz switching rate
• Adjustable switch current limit
• On-chip low battery detector
DESCRIPTION
The SC1633 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 83% can be easily achieved at 70mA 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 47µH to 150µH inductance are
recommended for most applications.
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
BLOCK DIAGRAM
APPLICATIONS
• Pocket organizers
• Electronic dictionaries
• Cameras
• Pagers
• Bar code scanners
• LCD displays
• Battery backup supplies
• Portable instruments
ORDERING INFORMATION
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
PIN CONFIGURATION TYPICAL APPLICATION CIRCUIT
DEVICE
(1)
VOLTAGE PACKAGE
SC1633CS
SC1633-3CS
SC1633-5CS
3.3V
3.0V
5.0V
SO-8
© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1633
January 29, 1998
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, TA = 25°C, VIN = 3.0V
Parameter V
IN
I
L
Min Typ Max Units
Input Voltage 1.8 7.0 V
Output Voltage
SC1633
SC1633-3
SC1633-5
I
L
= 70mA 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
SC1633/SC1633-3
SC1633-5
160
250
µA
Shutdown Mode Current 7 15 µA
Shutdown Recovery Time V
IN
=2.5V IL=70mA 1.8 msec
Efficiency
SC1633/SC1633-3
SC1633-5
I
L
=70mA 87
86
%
Line Regulation
SC1633
SC1633-3
SC1633-5
V
IN
=2.0 - 3.3V
V
IN
=2.0 - 3.0V
V
IN
=2.2 - 4.5V
I
L
=40mA 0.6
0.6
0.5
%V
OUT
Load Regulation
SC1633/SC1633-3
SC1633-5
I
L
=1mA - 70mA 0.6
0.5
%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”
SC1633/SC1633-3
SC1633-5
1.75
1.25
Ω
SW Off Leakage 1µA
Input Pin Bias Current 10 nA/Pin
Output Pin Leakage 10 nA/Pin
© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1633
January 29, 1998
TYPICAL PERFORMANCE CHARACTERISTICS
© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1633
January 29, 1998
TYPICAL PERFORMANCE CHARACTERISTICS (cont.)
APPLICATION EXAMPLES
Figure 1. 3V Output Step-Up Converter
© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1633
January 29, 1998
APPLICATION EXAMPLES (cont.)
Figure 2. 5V Output Step-Up Converter
Figure 3. 1-Cell Input 3V Output Step-Up Converter
Figure 4. 4-Cell Input Step-Up/Step-Down Converter
© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1633
January 29, 1998
APPLICATION EXAMPLES (cont.)
Figure 5. 3-Cell Input 3V Output Step-Down Converter
Figure 6. Boost-Drive 5V Output Step-Down Converter
© 1997 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
LOW VOLTAGE STEP-UP
DC-DC CONVERTER
SC1633
January 29, 1998
DEVICE OUTLINE - SO-8
PIN DESCRIPTIONS
PIN 1: I
LIM
/SD (1) Connected to VIN pin through a
resistor 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 SC1633 is limited by
the current limit resistor (see typical
performance characteristics). The
I
LIM
/SD pin should be shorted to VIN if
limiting switch peak current is not
required.
(2) The SC1633 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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