R1224N Series
PWM/VFM Step-down DC/DC Controller with Ext. Tr.
The R1224N Series are low supply current CMOS-based PWM/VFM step-down DC/DC controller with an external output transistor.
By simply using a power transistor, an inductor, a diode, and a capacitor as external components, a high-efficiency step-down DC/DC
converter can be easily configured. The PWM/VFM alternative circuit automatically switches to VFM control in the smaller output
current range and provides high efficiency even in the smaller output current range. The version with fixed PWM control and
adjustable output voltage with an external resistor is also available. The reset type protection circuit embedded into the device limits
output current by repeatedly triggering the soft start circuit when the oscillator maximum duty cycle continues for a predetermined
period of time. When the oscillator maximum duty cycle ends, normal operation is resumed automatically. R1224N also includes an
under-voltage lockout circuit (UVLO) that stops DC/DC operation and prevents malfunction when the supply voltage falls below the
UVLO detect voltage and reduces supply current.
FEATURES
• Supply Current (IDD1)·················· Typ. 20
μ
A (E, F, L, M Versions), Typ. 30
μ
A (G Version),
• Output Voltage Accuracy················ ± 2%
Typ. 40
μA (H Version) (VIN=VOUT=18.5V)
• Oscillator Frequency (fosc) ·············· 180kHz, 300kHz, 500kHz
• Standby Current (Istandby) ············ Max. 0.5μA (In standby)
•
··· Min. 100%
• Input Voltage Range (VIN)·········· 2.3V to 18.5V
• OUsVciLllaOtorDMeatxeimctumVoDltuatygCeyc(VleU(MVLaOx)d·u··ty··)···· Typ. 2.0V
• Output Voltage Range (VOUT)····· 1.2V to 6.0V (internally fixed R1224Nxx2E/F/L)
• Soft Start Time (tstart)······················· Typ. 10ms
Externally adjustable (Feedback voltage of 1.0V, R1224Nxx2G/H/M) • Reset Protection Circuit ················· Delay time for protection
Typ. 15ms
• Package ········································· SOT-23-5
BLOCK DIAGRAMS
R1224Nxx2E/F/L
R1224Nxx2G/H/M
(Internally fixed output voltage type)
(Externally adjustable output voltage type)
OSC
OSC
VIN
VIN
5
5
V
OUT
VFB
3
3
-
-
-
-
EXT
4
EXT
4
Amp
Amp
+
+
Vref
Vref
+
+
PWM/VFM
CONTROL
Soft Start
Soft Start
1
1
Chip Enable
CE
Chip Enable
CE
Protection
UVLO
Protection
+
-
+
-
Vref
Vref
UVLO
2
2
GND
GND
SELECTION GUIDE
TYPICAL APPLICATIONS
R1224Nxx2E/F/L
R1224Nxx2G/H/M
Package Quantity per Reel
SOT-23-5 3,000 pcs
Part No.
L
L
R1224N
.
xx.
2.
∗-TR-F
PMOS
PMOS
+
-
C1
R4
C4
R3
4
4
IN EXT
.
xx.
:
Specify the output voltage within the range
C1
5
1
3
IN EXT VOUT
5
1
3
V
VFB
V
1.2V (
.
12
.
) to 6.0V (
.60
.
) in 0.1V steps.
C3
C3
R1
R1
+
-
+
-
SD
SD
CE GND
2
CE GND
2
(For externally adjustable output voltage type, feedback voltage of 1.0V(
.
10
.
))
R2
.
.
:
Specify the oscillator frequency, modulation method, output
voltage adjustment.
∗
C2
C2
.
.
.
.
.
.
E
.
: 300kHz, PWM/VFM, fixed output voltage
: 500kHz, PWM/VFM, fixed output voltage
: 300kHz, fixed PWM, adjustable output voltage
: 500kHz, fixed PWM, adjustable output voltage
: 180kHz, PWM/VFM, fixed output voltage
CE CONTROL
CE CONTROL
F
.
PMOS : HAT1044M, L : 27μH,
SD : RB063L-30, C1 : 10μF, C2 : 0.1μF,
C3 : 47μF, R1 : 10Ω
PMOS : HAT1044M, L : 27μH,
SD : RB063L-30, C1 : 10μF, C2 : 0.1μF,
C3 : 47 F, C4 : 1000pF, R1 : 10 , R3 : 2.7k
Output voltage at 2.5V⋅⋅⋅R2 : 22kΩ, R4 : 33kΩ
G
H
.
.
μ
Ω
Ω,
L
.
M
.
:180kHz, fixed PWM, adjustable output voltage
PACKAGE (Top View)
TYPICAL CHARACTERISTIC
R1224N332E Efficiency vs. Output Current
SOT-23-5
5
4
VIN=7V, L=CDRH127(10μH)
100
90
80
70
60
50
40
30
20
10
0
1
2
3
1
2
3
4
5
CE
GND
VOUT or VFB
EXT
0.1
1
10
100
1000 10000
VIN
Output Current IOUT (mA)
APPLICATIONS
• Power source for hand-held communication equipment, cameras, and VCRs
• Power source for home appliances
• Power source for battery-powered equipment
No.EK-101-091101
Step-down DC/DC Converter