TC1142
M
Inductorless -2x Boost/Buck Regulator
Features
Package Type
• Input Range 2.5V to 5.5V
8-Pin MSOP
• Regulated Output Options from -3.0 to -5.0V
• Output Current 20mA (max)
V
CCLK
8
7
6
5
OUT
C2+
1
2
3
4
• 200kHz Internal Oscillator Frequency
• External Synchronizing Clock Input
• Logic Level Shutdown
V
IN
C1+
GND
- 1µA (max) Supply Current
• Available in 8-Pin MSOP Package
General Description
Applications
The TC1142 generates a regulated negative voltage
from -3V to -5V at 20mA from an input of 2.5V to 5.5V,
using only three external capacitors. Other boost/buck
switching regulators must use an inductor, which is
larger and radiates EMI. An internal voltage
comparator inhibits the charge pump when VOUT is
more negative than the regulated value (per the
ordering option). The values of flying capacitors C1 and
C2 are chosen to be less than COUT in order to reduce
the ripple generated from regulating VOUT in this
manner. The TC1142 also can be used as a -1x buck
regulator by omitting C2, and connecting the C2 pin to
• Cellular Phones
• Battery Powered/Portable Equipment
Device Selection Table
Output
Voltage Package
(V)*
Operating
Temp.
Range
Part
Number
TC1142-3.0EUA 3.0 8-Pin MSOP -40°C to +85°C
TC1142-4.0EUA 4.0 8-Pin MSOP -40°C to +85°C
TC1142-5.0EUA 5.0 8-Pin MSOP -40°C to +85°C
VOUT
.
*Other output voltages are available (-3.5V and -4.5V). Please
contact Microchip Technology Inc. for details.
The part goes into shutdown when the CCLK input is
driven low. When in shutdown mode, the part draws a
maximum of 1µA. When CCLK is pulled high, the part
runs from the internal 200kHz oscillator. The device
may be run with an external clock, provided the
frequency is greater than 3kHz and less than 500kHz.
The TC1142 comes in a space-saving MSOP package.
Functional Block Diagram
–2x Boost/Buck
–1x Buck
+
+
5.5V to 3V
5.5V to 2.5V
–
–
OFF
ON
OFF
ON
V
V
IN
IN
V
= -5.0V
V
= –3.0V
OUT
OUT
CCLK
CCLK
V
V
OUT
OUT
4.7µF
4.7µF
C
C
OSC
OVERRIDE
OSC
OVERRIDE
OUT
OUT
0.47µF
C1
0.47µF
0.47µF
C1
C2
TC1142-30
TC1142-50
C2–
GND
GND
2002 Microchip Technology Inc.
DS21360B-page 1