R1224N SERIES
PWM/VFM step-down DC/DC Converter
NO.EA-096-061102
OUTLINE
The R1224N Series are CMOS-based PWM step-down DC/DC Converter controllers with low supply current.
Each of these ICs consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier, a
phase compensation circuit, a soft-start circuit, a protection circuit, a PWM/VFM alternative circuit, a chip enable
circuit, resistors for output voltage detect, and input voltage detect circuit. A low ripple, high efficiency step-down
DC/DC converter can be easily composed of this IC with only several external components, or a power-transistor,
an inductor, a diode and capacitors. Output Voltage is fixed or can be adjusted with external resistors (Adjustable
types are without PWM/VFM alternative circuit).
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. Several
types of the R1224Nxxx, which are without a PWM/VFM alternative circuit, are also available.
If the term of maximum duty cycle keeps on a certain time, the embedded protection circuit works. The
protection circuit 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. When the cause of large load current or something
else is removed, the operation is automatically released and returns to normal operation.
Further, built-in UVLO function works when the input voltage is equal or less than UVLO threshold, it makes
this IC be standby and suppresses the consumption current and avoid an unstable operation.
FEATURES
•
Supply Current ................................................................ Typ. 20µA (R1224Nxx2E/F/M/L, R1224N102M)
Typ. 30µA (R1224Nxx2G, R1224N102G)
Typ. 40µA (R1224Nxx2H, R1224N102H)
•
Standby Current .............................................................. Typ. 0µA
•
Input Voltage Range ....................................................... 2.3V~18.5V
•
Output Voltage Range..................................................... 1.2V to 6.0V (R1224Nxx2x)
1.0V to V
IN
(R1224N102x)
•
Output Voltage Accuracy.................................................
±2.0%
•
Oscillator Frequency ....................................................... Typ. 180kHz (R1224Nxx2M, R1224N102M)
Typ. 300kHz (R1224Nxx2E/G, R1224N102G)
Typ. 500kHz (R1224Nxx2F/H, R1224N102H)
•
Efficiency......................................................................... Typ. 90%
•
Low Temperature-Drift Coefficient of Output Voltage...... Typ.
±100ppm/°C
•
Package .......................................................................... SOT-23-5
•
Built-in Soft-start Function............................................... Typ. 10ms
•
Built-in Current Limit Circuit
APPLICATIONS
•
Power source for hand-held communication equipment, cameras, video instruments such as VCRs,
camcorders.
•
Power source for battery-powered equipment.
•
Power source for household electrical appliances.
1
R1224N
BLOCK DIAGRAM
*Fixed Output Voltage Type
V
IN
5
OSC
3
V
OUT
EXT
4
PWM/VFM
CONTROL
Amp
Vref
Soft Start
Protection
UVLO
Chip Enable
Vref
1
CE
2
GND
*Adjustable Output Voltage Type
V
IN
5
OSC
3
V
FB
EXT
4
Amp
Vref
Soft Start
Protection
UVLO
Chip Enable
Vref
1
CE
2
GND
2
R1224N
SELECTION GUIDE
In the R1224N 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 with designating the part number as shown below;
R1224Nxx2x-xx-x
←Part
Number
↑ ↑ ↑↑ ↑ ↑
a b cd e f
Code
a
b
c
Contents
Designation of Package Type;
N: SOT-23-5
Setting Output Voltage (V
OUT
):
Stepwise setting with a step of 0.1V in the range of 1.2V to 6.0V is possible.
Adjustable type; a=10 means Reference Voltage=1.0V Optional Function is G/H/M.
2: fixed
Designation of Optional Function
E : 300kHz, with a PWM/VFM alternative circuit
F : 500kHz, with a PWM/VFM alternative circuit
G : 300kHz, without a PWM/VFM alternative circuit
H : 500kHz, without a PWM/VFM alternative circuit
L : 180kHz, with a PWM/VFM alternative circuit
M :180kHz, without a PWM/VFM alternative circuit
Designation of Taping Type;
(Refer to Taping Specification)"TR" is prescribed as a standard.
Designation of Composition of pin plating
-F: Lead free plating
d
e
f
3
R1224N
PIN CONFIGURATIO
•
5
SOT-23-5
4
(mark side)
1
2
3
PIN DESCRIPTION
Pin No
1
2
3
4
5
Symbol
CE
GND
V
OUT
(V
FB
)
EXT
V
IN
Pin Description
Chip Enable Pin (“H” Active)
Ground Pin
Pin for Monitoring Output Voltage (Feedback Voltage)
External Transistor Drive Pin (CMOS Output)
Power Supply Pin
ABSOLUTE MAXIMUM RATINGS
Symbol
V
IN
V
EXT
V
CE
V
OUT
I
EXT
P
D
Topt
Tstg
V
IN
Supply Voltage
EXT Pin Output Voltage
CE Pin Input Voltage
V
OUT
/V
FB
Pin Input Voltage
EXT Pin Inductor Drive Output Current
Power Dissipation (SOT-23-5)*
Operating Temperature Range
Storage Temperature Range
Item
Rating
20
−0.3
to V
IN
+0.3
−0.3
to V
IN
+0.3
−0.3
to V
IN
+0.3
±
50
420
−40
to
+85
−55
to
+125
Unit
V
V
V
V
A
mW
°C
°C
* ) For Power Dissipation, please refer to PACKAGE INFORMATION to be described.
4
R1224N
ELECTRICAL CHARACTERISTICS
•
R1224Nxx2X (X=E/F/G/H/L/M) except R1224N102X
Item
Operating Input Voltage
Step-down Output Voltage
Step-down Output Voltage
Temperature Coefficient
V
IN
=V
CE
=V
SET
+1.5V,
I
OUT
=−100mA
When V
SET
<
1.5V, V
IN
=V
CE
=3.0V
=
−40°C
<
Topt
<
85°C
=
=
V
IN
=V
CE
=V
SET
+1.5V,
I
OUT
=−100mA
When V
SET
<
1.5, V
IN
=V
CE
=3.0V
=
L/M Version
E/G Version
F/H Version
−40°C
<
Topt
<
85°C
=
=
V
IN
=V
CE
=V
OUT
=18.5V
E/F/L/M Version
G version
H version
V
IN
=18.5V,
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
=V
CE
=V
OUT
=18.5V
V
IN
=V
OUT
=18.5V,
V
CE
=0V
V
IN
=8V,
V
OUT
=0V
V
IN
=8V,
V
OUT
=0V
100
E/F/L Version
V
IN
=V
CE
=2.5V
to 1.5V, V
OUT
=0V
V
IN
=V
CE
=1.5V
to 2.5V, V
OUT
=0V
V
IN
=V
SET
+1.5V,
I
OUT
=−10mA
V
CE
=0V→V
SET
+1.5V
V
IN
=V
CE
=V
SET
+1.5V
V
OUT
=V
SET
+1.5V→0V
5
5
1.8
35
2.0
V
UVLO1
+0.1
10
15
2.2
2.3
20
30
−0.5
1.5
0.3
20
Conditions
Min.
2.3
V
SET
×0.98
V
SET
±100
Typ.
V
IN
V
OUT
∆
V
OUT
/
∆
Topt
Topt=25°C
Symbol
Max.
18.5
V
SET
×1.02
Unit
V
V
ppm/°C
fosc
Oscillator Frequency
144
240
400
180
300
500
±0.2
20
30
40
0.0
−17
30
0.0
0.0
216
360
600
kHz
∆
fosc/
∆
Topt
Oscillator Frequency
Temperature Coefficient
Supply Current 1
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
UVLO Voltage
UVLO Release Voltage
Delay Time by Soft-Start function
Delay Time for protection circuit
%/°C
50
60
80
0.5
−10
I
DD1
Istandby
I
EXTH
I
EXTL
I
CEH
I
CEL
V
CEH
V
CEL
Maxdty
VFMdty
V
UVLO1
V
UVLO2
tstart
tprot
µA
µA
mA
mA
0.5
µA
µA
V
V
%
%
V
V
ms
ms
5
