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| TC105 Datasheet, PDF (1/14 Pages) Microchip Technology – PFM/PWM Step-Down DC/DC Controller | |||
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TC105
PFM/PWM Step-Down DC/DC Controller
Features
⢠57µA (Typ) Supply Current
⢠1A Output Current
⢠0.5µA Shutdown Mode
⢠300kHz Switching Frequency for Small Inductor
Size
⢠Programmable Soft-Start
⢠92% Typical Efficiency
⢠Small Package: 5-Pin SOT-23A
Applications
⢠Palmtops
⢠Battery-Operated Systems
⢠Portable Instruments
⢠Positive LCD Bias Generators
⢠Portable Communicators
⢠Hand-Held Scanners
⢠5V to 3V Down Converters
Device Selection Table
Part
Number
Output
Voltage
(V)*
Package
Osc.
Freq.
(kHz)
Operating
Temp.
Range
TC105503ECT 5.0 5-Pin SOT-23A 300 -40°C to +85°C
TC105333ECT 3.3 5-Pin SOT-23A 300 -40°C to +85°C
TC105303ECT 3.0 5-Pin SOT-23A 300 -40°C to +85°C
*Other output voltages are available. Please contact
Microchip Technology Inc. for details.
Package Type
5-Pin SOT-23A
VOUT
5
SHDN
4
TC105
1
EXT
2
VDD
3
GND
NOTE: 5-Pin SOT-23A is equivalent to the EIAJ SC-74A
General Description
The TC105 is a step-down (Buck) switching controller
that furnishes output currents of up to 1A (max) while
delivering a typical efficiency of 92%. The TC105
normally operates in pulse width modulation mode
(PWM), but automatically switches to pulse frequency
modulation (PFM) at low output loads for greater
efficiency. Oscillator frequency is 300kHz, allowing use
of small (22µH) inductors. Supply current draw is only
102µA (max), and is reduced to less than 0.5µA when
the SHDN input is brought low. Regulator operation is
suspended during shutdown. The TC105 accepts a
maximum input voltage of 10V.
The TC105 is available in a small 5-Pin SOT-23A
package, occupies minimum board space and is ideal
for a wide range of applications.
Functional Block Diagram
D1
MA737
L1 22µH (Sumida CD54)
5
4
VOUT
SHDN
TC105333ECT
EXT
VDD
GND
1
2
3
RSS 470K
OFF ON
CSS
(From System
Control Logic)
0.033µF
3.3V
VOUT
C2
47µF
10V
Tantalum
Si 9430 P
+
VBATT
6V â
NiMH
C1 10µF/16V
3.3V Regulated Supply Using 6V
NiMH Battery Pack Input
© 2002 Microchip Technology Inc.
DS21349B-page 1
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