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Número de pieza | TCM829 | |
Descripción | Switched Capacitor Voltage Converters | |
Fabricantes | Microchip Technology | |
Logotipo | ||
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No Preview Available ! TCM828
TCM829
Switched Capacitor Voltage Converters
FEATURES
s Charge Pump in 5-Pin SOT-23A Package
s >95% Voltage Conversion Efficiency
s Voltage Inversion and/or Doubling
s Low 50µA (TCM828) Quiescent Current
s Operates from +1.5V to +5.5V
s Up to 25mA Output Current
s Only Two External Capacitors Required
APPLICATIONS
s LCD Panel Bias
s Cellular Phones
s Pagers
s PDAs, Portable Dataloggers
s Battery-Powered Devices
PIN CONFIGURATION
*5-Pin SOT-23A
OUT 1
5 C+
VIN 2 TCM828ECT
TCM829ECT
GENERAL DESCRIPTION
The TCM828/829 are CMOS “charge-pump” voltage
converters in ultra-small 5-Pin SOT-23A packages. They
invert and/or double an input voltage which can range from
+1.5V to +5.5V. Conversion efficiency is typically >95%.
Switching frequency is 12kHz for the TCM828 and 35kHz for
the TCM829.
External component requirement is only two capacitors
(3.3µF nominal) for standard voltage inverter applications.
With a few additional components a positive doubler can
also be built. All other circuitry, including control, oscillator,
power MOSFETs are integrated on-chip. Supply current
is 50µA (TCM828) and 115µA (TCM829).
The TCM828 and TCM829 are available in a 5-Pin
SOT-23A surface mount package.
ORDERING INFORMATION
Part No.
Package
Temp. Range
TCM828ECT
5-Pin SOT-23A
– 40°C to +85°C
TCM829ECT
5-Pin SOT-23A
– 40°C to +85°C
NOTE: 5-Pin SOT-23A is equivalent to EIAJ SC-74A.
C– 3
4 GND
NOTE: *5-Pin SOT-23A is equivalent to EIAJ SC-74A
TYPICAL OPERATING CIRCUIT
Voltage Inverter
C+ VIN
C1
C–
TCM828
TCM829
GND
OUT
INPUT
V–
OUTPUT
C2
© 2001 Microchip Technology Inc. DS21488A
TCM828/829-4 5/22/00
1 page Switched Capacitor
Voltage Converters
TCM828
TCM829
ROUT =
R
OUT
OF
SINGLE DEVICE
NUMBER OF DEVICES
VI+N . . .
22
33
C1
4
TCM828
C1
4 TCM828
TCM829
TCM829
5 "1"
1
5
"n"
...
1
VOUT
...
VOUT = VI–N
C2
Figure 5. Paralleling TCM828s or TCM829s to Reduce Output Resistance
Voltage Doubler/Inverter
Another common application of the TCM828/829 is
shown in Figure 6. This circuit performs two functions in
combination. C1 and C2 form the standard inverter circuit
described above. C3 and C4 plus the two diodes form the
voltage doubler circuit. C1 and C3 are the pump capacitors
and C2 and C4 are the reservoir capacitors. Because both
sub-circuits rely on the same switches if either output is
loaded, both will droop toward GND. Make sure that the total
current drawn from both the outputs does not total more
than 40mA.
Diode Protection for Heavy Loads
When heavy loads require the OUT pin to sink large
currents being delivered by a positive source, diode protec-
tion may be needed. The OUT pin should not be allowed to
be pulled above ground. This is accomplished by connect-
ing a Schottky diode (1N5817) as shown in Figure 7.
4
GND
TCM828
TCM829
OUT 1
Figure 7. High V– Load Current
Layout Considerations
As with any switching power supply circuit good layout
practice is recommended. Mount components as close
together as possible to minimize stray inductance and
capacitance. Also use a large ground plane to minimize
noise leakage into other circuitry.
V+IN
D1, D2 = 1N4148
32
C1
4 TCM828
TCM829
D1
51
VOUT = VI–N
C2
D2
VOUT = (2VIN) –
C3 (VFD1) – (VFD2)
C4
Figure 6. Combined Doubler and Inverter
© 2001 Microchip Technology Inc. DS21488A
5
TCM828/829-4 5/22/00
5 Page |
Páginas | Total 9 Páginas | |
PDF Descargar | [ Datasheet TCM829.PDF ] |
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