© 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 VIN 7.0 V
Operating
Temperature Range TA0 to 70 °C
Storage
Temperature Range TSTG -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 VIN ILMin Typ Max Units
Input Voltage 1.8 7.0 V
Output Voltage
SC1633
SC1633-3
SC1633-5
IL = 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 VIN=2.5V IL=70mA 1.8 msec
Efficiency
SC1633/SC1633-3
SC1633-5 IL=70mA 87
86 %
Line Regulation
SC1633
SC1633-3
SC1633-5
VIN=2.0 - 3.3V
VIN=2.0 - 3.0V
VIN=2.2 - 4.5V
IL=40mA 0.6
0.6
0.5
%VOUT
Load Regulation
SC1633/SC1633-3
SC1633-5 IL=1mA - 70mA 0.6
0.5 %VOUT
Oscillator Frequency 90 120 150 kHz
LBI Pin Trip Point 1.17 1.22 1.27 V
LBO “On Resistance” VIN = 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: ILIM/SD (1) Connected to VIN pin through a
resistor to set the switch peak current.
It serves to protect the IC and induc-
tor, 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
ILIM/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 ILIM/SD pin is pulled to
ground.
PIN 2: VIN 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 Resis-
tance” at VIN=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: VOUT The output voltage feeds back to the
IC through this pin.
PIN CONFIGURATION
