POWER SUPPLY
S-8430AF
STEP-UP & DOWN VOLTAGE REGULATOR
Consisting of an RC oscillation circuit, a switching regulator, a
voltage regulator and a Schottky diode, this DC-DC Converter
performs two functions. It serves as a voltage regulator when
the input voltage is higher than the output. When the input
voltage is lower than the output, it serves as a step-up switch-
ing regulator and a voltage regulator. Therefore, the output
level is kept constant. The output voltage can be changed from
3V to 5V, and vice versa by an external signal. The S-8430AF
is provided with a shutdown function that stops an internal RC
oscillation circuit by other external signal.
FEATURES
• Low current consumption
• High-precision output voltage
• Low voltage operation
• Selectable output voltage (switchable from 3V to 5V, and vice
versa)
• Built-in RC oscillating circuit
• Shutdown function
• Selectable output voltage at shutdown (switchable from GND
to voltage near the input voltage, and vice versa)
• Built-in Shottky-diode
APPLICATIONS
• Compact camera
• Pager
• Battery-powered devices
• Handy copier
• Handy terminal
PIN CONFIGURATIONS
SPECIFICATIONS
(Ta=25 ºC
)
8-pin SOP
Operation start-up
voltage
Parameter
Input voltage
Output voltage
Current consumption
oscillation frequency
Top view
V
IN=3V
V
IN=3V
VIN=7V
V
IN=2V
No load
I
OUT=30mA
I
OUT=30mA
V
IN
1
2
3
4
8
7
6
5
VSS
No load, SEL2=High
Conditions
SEL2=Low
>
V
IN=3V
SEL1=Low
SEL2=Low
SEL2=High
SEL1=High
V
OUT = 2V
ON/OFF
SEL1
CONT
ON/OFF=Low
ON/OFF=High
ON/OFF=High
ON/OFF=High
V
V
SW
4.80 V
Min.
2.85 V
3.00 V
3.15 V
0.9V
20kHz
40kHz
70kHz
Rating
Typ.
SEL2
OUT
5.00 V
5.20 V
11µA
25µA
0.2µA
Max.
10.0 V
S-8437/8438 Series
INVERTING SWITCHING REGULATOR
Consisting of a reference voltage source, an RC oscillation
circuit, a power MOSFET and an error amplifier, the output
voltage of the devices is fixed internally (for S-8437) or adjust-
able (for S-8438) . For the S-8437AF, the output voltage is fixed
internally and it easily forms an inverting switching regulator
with shutdown function; using an external coil, a diode and a
capacitor. For the S-8438AF, any output voltage can be set
under the conditions of VIN≤20- -VOUT by adding two external
resistors in addition to the above parts. Both the S-8437AF and
the S-8438AF are suitable for use as power sources for por-
table devices because of their small 5-pin package (SOT-89-5),
low current consumption and few external parts.
FEATURES
• Low current consumption (S-8437AF)
Operating
Shutdown
• High-precision output voltage
Any voltage can be set by mounting two external resistors (S-8438AF).
• Built-in CR oscillation circuit
Oscillation frequency
: 13µA typ.
: 0.1µA max.
: -5V±3.5%(S-8437AF)
•
: 50kHz typ.
• Built-in power MOS FET
• SOT-89-5 package
I
I
APPLICATIONS
• Power supply for portable instruments, such as pagers, cal-
culators, and remote controllers
• Constant voltage power for LCDs and analog circuits
• Power supply for communications equipment, such as
cordless phone and portable telephone
SPECIFICATIONS
S-8437AF-ZA-T1/T2
Parameter
S-8438AF-ZB-T1/T2
Parameter
Conditions
Min.
Typ.
Max.
Unit
Conditions
Min.
Typ.
Max.
Unit
2
10
-5.175
28
V
V
Input voltage*
2
10
1.224
19
V
V
Input voltage*
V
V
V
V
V
IN=5V, IOUT=10mA
IN=5V, VOUT=-7V
IN=5V, ON/OFF="L"
IN=5V
-4.825
-5.000
13
Output voltage
Reference voltage
Current consumption
Oscillation frequency
Switching current
1.176
1.200
9
V
V
V
V
IN=5V
µA
µA
kHz
mA
Current consumption
Standby current
Oscillation frequency
Switching current
µA
kHz
mA
IN=5V, VFB= -0.3V
IN=5V
0.1
30
50
70
30
50
70
150
IN=5V, CONT=4V
IN=5V, CONT=4V
150
The following equation shall be met VIN
≤ 20-I-VOUTI
*
The following equation shall be met VIN ≤ 20-I-VOUT
BLOCK DIAGRAM
S-8437AF
I
*
PIN CONFIGULATIONS
SOT-89-5
Top view
5
4
S-8438AF
-VOUT
CONT
CONT
VIN
V
IN
R1
+
-
1
2
3
+
-
VFB
Control circuit
Oscillation circuit
Control circuit
Oscillation circuit
Pin No. S-8437 S-8438
R2
1
2
3
4
5
CONT
V
ON/OFF
-VOUT
SS
ON/OFF
Reference voltage
circuit
Reference voltage
circuit
V
REF
V
FB
VREF
V
IN
VSS
V
SS
18
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