鈥?/div>
Palmtops
Battery-Operated Systems
Portable Instruments
Positive LCD Bias Generators
Portable Communicators
Hand-Held Scanners
5V to 3V Down Converters
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 (22碌H) inductors. Supply current draw is only
102碌A(chǔ) (max), and is reduced to less than 0.5碌A(chǔ) 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.
Device Selection Table
Part
Number
TC105503ECT
TC105333ECT
TC105303ECT
Output
Voltage
(V)*
5.0
3.3
3.0
Package
5-Pin SOT-23A
5-Pin SOT-23A
5-Pin SOT-23A
Osc.
Freq.
(kHz)
300
300
300
Operating
Temp.
Range
-40擄C to +85擄C
-40擄C to +85擄C
-40擄C to +85擄C
*Other output voltages are available. Please contact
Microchip Technology Inc. for details.
Functional Block Diagram
L
1
22碌H (Sumida CD54)
R
SS
470K
D
1
MA737
C
SS
0.033碌F
3.3V
V
OUT
OFF ON
(From System
Control Logic)
5
V
OUT
4
SHDN
C2
47碌F
10V
Tantalum
TC105333ECT
EXT
V
DD
GND
1
2
3
Si 9430
P
+
V
BATT
6V 鈥?/div>
NiMH
C
1
10碌F/16V
3.3V Regulated Supply Using 6V
NiMH Battery Pack Input
2002 Microchip Technology Inc.
DS21349B-page 1
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