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OUTLINE
‘99.12.8
PWM/VFM step-down DC/DC Converter
R1223N Series
The R1223N Series are PWM step-down DC/DC Converter controllers with low supply current by CMOS
process.
Each of these ICs consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier,
a soft-start circuit, a protection circuit, a PWM/VFM alternative circuit, a chip enable circuit, and resistors for
voltage detection. A low ripple, high efficiency step-down DC/DC converter can be easily composed of this IC
with only four external components, or a power-transistor, an inductor, a diode and a capacitor.
With a PWM/VFM alternative circuit, when the load current is small, the operation is automatically switching
into the VFM oscillator from PWM oscillator, therefore the efficiency at small load current is improved. The
R1223N XXXB type, which is without a PWM/VFM alternative circuit, is also available.
If the term of maximum duty cycle keeps on a certain time, the embedded protection circuit works. There are
two types of protection function. One is latch-type protection circuit, and it works to latch an external Power
MOSFET with keeping it disable. To release the condition of protection, after disable this IC with a chip enable
circuit, enable it again, or restart this IC with power-on. The other is Reset-type protection circuit, and it works to
restart the operation with soft-start and repeat this operation until maximum duty cycle condition is released.
Either of these protection circuits can be designated by users’ request.
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FEATURES
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Range of Input Voltage
· · · · · · · · · · · · ·2.3V~13.2V
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Built-in Soft-start Function and Two choices of Protection Function (Latch-type or Reset type)
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Two choices of Oscillator Frequency
· · · · · ·300kHz,
500kHz
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High Efficiency
· · · · · · · · · · · · · · · · · ·TYP.
90%
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Output Voltage
· · · · · · · · · · · · · · · · ·
Stepwise Setting with a step of 0.1V
in the range of 1.5V
~
5.0V
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Standby Current
· · · · · · · · · · · · · · · · ·TYP.
0µA
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High Accuracy Output Voltage
· · · · · · · · · ·±2.0%
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Low Temperature-Drift Coefficient of Output Voltage
· · · · ·
TYP. ±100ppm/°C
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APPLICATIONS
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Power source for hand-held communication equipment, cameras, video instruments such as VCRs,
camcorders.
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Power source for battery-powered equipment.
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Power source for household electrical appliances.
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Rev. 1.11
-1-
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BLOCK DIAGRAM
V
IN
OSC
V
OUT
Vref
EXT
PWM/VFM
CONTROL
Protection
Soft Start
Chip Enable
CE
GND
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SELECTION GUIDE
In the R1223N Series, the output voltage, the oscillator frequency, the optional function, and the taping type for
the ICs can be selected at the user’s request.
The selection can be made by designating the part number as shown below;
R1223NXXXX-XX
- -- -
a
b c
Code
a
b
c
d
Contents
d
Setting Output Voltage(V
OUT
):
Stepwise setting with a step of 0.1V in the range of 1.5V to 5.0V is possible.
Designation of Oscillator Frequency
2 : fixed
Designation of Optional Function
A : 300kHz, with a PWM/VFM alternative circuit, Latch-type protection
B : 500 kHz, with a PWM/VFM alternative circuit, Latch-type protection
C : 300kHz, without a PWM/VFM alternative circuit, Latch-type protection
D : 500kHz, without a PWM/VFM alternative circuit, Latch-type protection
E : 300kHz, with a PWM/VFM alternative circuit, Reset-type protection
F : 500 kHz, with a PWM/VFM alternative circuit, Reset-type protection
G : 300kHz, without a PWM/VFM alternative circuit, Reset-type protection
H : 500kHz, without a PWM/VFM alternative circuit, Reset-type protection
Designation of Taping Type; Ex. :TR,TL(refer to Taping Specification)
”TR” is prescribed as a standard.
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Rev. 1.11
-2-
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PIN CONFIGURATION
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SOT-23-5
5
V
IN
4
EXT
(mark side)
CE GND V
OUT
1
2
3
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PIN DESCRIPTION
Pin No.
1
2
3
4
5
Symbol
CE
GND
V
OUT
EXT
V
IN
Chip Enable Pin
Ground Pin
Pin for Monitoring Output Voltage
External Transistor Drive Pin
Power Supply Pin
Description
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ABSOLUTE MAXIMUM RATINGS
Symbol
V
IN
V
EXT
V
CE
V
OUT
I
EXT
PD
Topt
Tstg
Item
V
IN
Supply Voltage
EXT Pin Output Voltage
CE Pin Input Voltage
V
OUT
Pin Input Voltage
EXT Pin Inductor Drive Output Current
Power Dissipation
Operating Temperature Range
Storage Temperature Range
Rating
15
-0.3~V
IN
+0.3
-0.3~V
IN
+0.3
-0.3~V
IN
+0.3
±25
250
-40~+85
-55~+125
Unit
V
V
V
V
mA
mW
°C
°C
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Rev. 1.11
-3-
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ELECTRICAL CHARACTERISTICS
lR1223N**2A(,C,E,G)
Output Voltage : Vo
Symbol
V
IN
V
OUT
Item
Operating Input Voltage
Step-down Output Voltage
V
IN
=V
CE
=Vo+1.2V,I
OUT
=-10mA
Conditions
MIN.
2.3
Vo´
0.98
DV
OUT
/
DT
fosc
Df
OSC
/
DT
I
DD1
I
stb
I
EXTH
I
EXTL
I
CEH
I
CEL
V
CEH
V
CEL
Maxdty
VFMdty
T
start
Step-down Output Voltage
Temperature Coefficient
Oscillator Frequency
Oscillator Frequency
Temperature Coefficient
Supply Current1
Standby Current
EXT "H" Output Current
EXT "L" Output Current
CE "H" Input Current
CE "L" Input Current
CE "H" Input Voltage
CE "L" Input Voltage
Oscillator Maximum Duty Cycle
VFM Duty Cycle
Delay Time by Soft-Start function
(Topt=25°C)
TYP.
MAX. Unit
13.2
Vo
Vo´
1.02
±100
ppm
/°C
V
V
-40°C
£
Topt
£
85°C
V
IN
=V
CE
=Vo+1.2V,I
OUT
=-100mA
-40°C
£
Topt
£
85°C
240
300
±0.3
360
kHz
%
/°C
V
IN
=13.2V,V
CE
=13.2V,V
OUT
=13.2V
V
IN
=13.2V,V
CE
=0V,V
OUT
=0V
V
IN
=8V,V
EXT
=7.9V,V
OUT
=8V,V
CE
=8V
V
IN
=8V,V
EXT
=0.1V,V
OUT
=0V,V
CE
=8V
V
IN
=13.2V,V
CE
=13.2V,V
OUT
=13.2V
V
IN
=13.2V,V
CE
=0V,V
OUT
=13.2V
V
IN
=8V,V
OUT
=0V®1.5V
V
IN
=8V,V
OUT
=1.5V®0V
0.3
100
only for A, E version
V
IN
= Vo+1.2V, V
CE
=0V®Vo+1.2V
specified at 80% for rising edge
5
-0.5
10
100
0
-10
20
0
0
0.8
0.8
160
0.5
-6
mA
mA
mA
mA
0.5
mA
mA
1.2
V
V
%
25
10
16
%
ms
T
prot
Delay Time for protection circuit
V
IN
=V
CE
=Vo+1.2V
V
OUT
= Vo+1.2V®0V
1
3
5
ms
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Rev. 1.11
-4-
lR1223N**2B(,D,F,H)
Output Voltage : Vo
Symbol
V
IN
V
OUT
Item
Operating Input Voltage
Step-down Output Voltage
V
IN
=V
CE
=Vo+1.2V,I
OUT
=-10mA
Conditions
MIN.
2.3
Vo´
0.98
DV
OUT
/
DT
fosc
Df
OSC
/
DT
I
DD1
I
stb
I
EXTH
I
EXTL
I
CEH
I
CEL
V
CEH
V
CEL
Maxdty
VFMdty
T
start
Step-down Output Voltage
Temperature Coefficient
Oscillator Frequency
Oscillator Frequency
Temperature Coefficient
Supply Current1
Standby Current
EXT "H" Output Current
EXT "L" Output Current
CE "H" Input Current
CE "L" Input Current
CE "H" Input Voltage
CE "L" Input Voltage
Oscillator Maximum Duty Cycle
VFM Duty Cycle
Delay Time by Soft-Start function
(Topt=25°C)
TYP.
MAX. Unit
13.2
Vo
Vo´
1.02
±100
ppm
/°C
V
V
-40°C
£
Topt
£
85°C
V
IN
=V
CE
=Vo+1.2V,I
OUT
=-100mA
-40°C
£
Topt
£
85°C
400
500
±0.3
600
kHz
%
/°C
V
IN
=13.2V,V
CE
=13.2V,V
OUT
=13.2V
V
IN
=13.2V,V
CE
=0V,V
OUT
=0V
V
IN
=8V,V
EXT
=7.9V,V
OUT
=8V,V
CE
=8V
V
IN
=8V,V
EXT
=0.1V,V
OUT
=0V,V
CE
=8V
V
IN
=13.2V,V
CE
=13.2V,V
OUT
=13.2V
V
IN
=13.2V,V
CE
=0V,V
OUT
=13.2V
V
IN
=8V,V
OUT
=0V®1.5V
V
IN
=8V,V
OUT
=1.5V®0V
0.3
100
only for B, F version
V
IN
= Vo+1.2V, V
CE
=0V® Vo+1.2V
specified at 80% for rising edge
3
-0.5
10
140
0
-10
20
0
0
0.8
0.8
200
0.5
-6
mA
mA
mA
mA
0.5
mA
mA
1.2
V
V
%
25
6
10
%
ms
T
prot
Delay Time for protection circuit
V
IN
=V
CE
=Vo+1.2V
V
OUT
= Vo+1.2V®0V
1
2
4
ms
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Rev. 1.11
-5-
