R1232D SERIES
PWM/VFM STEP-DOWN DC/DC CONVERTER WITH SYNCHRONOUS RECTIFIER
NO.EA-129-0604
OUTLINE
The R1232D Series are CMOS-based PWM step-down DC/DC converters with synchronous rectifier, low
supply current. As an output capacitor, a 10µF or more ceramic capacitor can be used with the R1232D.
Each of these ICs consists of an oscillator, a PWM control circuit, a voltage reference unit, an error amplifier, a
soft-start circuit, protection circuits, a protection against miss operation under low voltage (UVLO), PWM/VFM
alternative circuit, a chip enable circuit, a synchronous rectifier, Nch. driver transistor, and so on. A low ripple,
high efficiency step-down DC/DC converter can be easily composed of this IC with only a few kinds of external
components, or an inductor and capacitors. (As for R1232D001x type, divider resistors are also necessary.) In
terms of Output Voltage, it is fixed internally in the R1232Dxx1x types. While in the R1232D001x types, Output
Voltage is adjustable with external divider resistors.
PWM/VFM alternative circuit is active with Mode Pin of the R1232D Series. Thus, when the load current is
small, the operation can be switching into the VFM operation from PWM operation by the logic of MODE pin and
the efficiency at small load current can be improved. As protection circuits, current limit circuit which limits peak
current of L
X
at each clock cycle, and latch type protection circuit which works if the term of the over-current
condition keeps on a certain time in PWM mode exist. Latch-type protection circuit works to latch an internal
driver 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 or make the supply voltage at UVLO detector threshold level or
lower than UVLO.
FEATURES
•
Two choices of Oscillator Frequency ............................ 1MHz, 2.25MHz
(Small inductors can be used. 4.7µH for 1MHz/2.2µH for 2.25MHz)
•
Built-in Driver ON Resistance ....................................... P-channel 0.2Ω (at V
IN
=5.0V)
•
Built-in Soft-start Function............................................. Typ. 1.0ms (fosc=1MHz type)
•
Output Voltage .............................................................. 0.9V to 3.3V (xx1x Type)
0.8V to V
IN
(001x Type)
•
High Accuracy Output Voltage ......................................±2.0% (PWM Mode)
•
Built-in Current Limit Circuit .......................................... Typ. 1.4A
•
Package ........................................................................SON-8 (t=0.9mm)
APPLICATIONS
•
Power source for portable equipment such as cellular, PDA, DSC, Notebook PC.
•
Power source for HDD
1
R1232D
SELECTION GUIDE
In the R1232D Series, the output voltage, the oscillator frequency, 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;
R1232Dxx1x-xx
↑ ↑↑ ↑
a bc d
Code
a
b
←Part
Number
Contents
Setting Output Voltage(V
OUT
):
Stepwise setting with a step of 0.1V in the range of 0.9V to 3.3V is possible for fixed
output version."00" is for Output Voltage Adjustable version
(0.8V as the feedback voltage.)
1 : fixed
Designation of Optional Function
A : 1MHz, Fixed Output Voltage
B : 2.25MHz, Fixed Output Voltage
C : 1MHz, Adjustable Output Voltage
D : 2.25MHz, Adjustable Output Voltage
Designation of Taping Type;
(Refer to Taping Specification)"TR" is prescribed as a standard.
c
d
3
R1232D
PIN CONFIGURATION
SON-8
Top View
8
7
6
5
Bottom View
5
6
7
8
1
2
3
4
4
3
2
1
PIN DESCRIPTIONS
Pin No
1
2
3
4
5
6
7
8
Symbol
PGND
V
IN
V
DD
CE
V
OUT
/V
FB
MODE
AGND
L
X
Ground Pin
Voltage Supply Pin
Voltage Supply Pin
Chip Enable Pin (active with "H")
Output/Feedback Pin
Mode changer Pin (PWM mode at "L", VFM mode at "H".)
Ground Pin
L
X
Switching Pin (CMOS Output)
Pin Description
∗
Tab in the
parts have GND level. (They are connected to the reverse side of this IC.)
Do not connect to other wires or land patterns.
ABSOLUTE MAXIMUM RATINGS
Symbol
V
IN
V
DD
V
LX
V
CE
V
MODE
V
FB
I
LX
P
D
Topt
Tstg
V
IN
Supply Voltage
V
DD
Pin Voltage
L
X
Pin Voltage
CE Pin Input Voltage
MODE Pin Input Voltage
V
FB
Pin Input Voltage
L
X
Pin Output Current
Power Dissipation (SON-8)*
1
Operating Temperature Range
Storage Temperature Range
Item
Rating
6.5
6.5
−0.3
to V
IN
+
0.3
−0.3
to V
IN
+
0.3
−0.3
to V
IN
+
0.3
−0.3
to V
IN
+
0.3
±1.5
480
−40
to 85
−55
to 125
Unit
V
V
V
V
V
V
V
mW
°C
°C
∗1)
For Power Dissipation please refer to PACKAGE INFORMATION to be described.
4
R1232D
ELECTRICAL CHARACTERISTICS
•
R1232DxxxA/C
Topt=25°C
Symbol
V
IN
Item
Operating Input Voltage
Step-down Output Voltage
(PWM Mode)
Step-down Output Voltage
(VFM Mode)
Conditions
Min.
2.6
Typ.
Max.
5.5
Unit
V
R1232Dxx1A, MODE=”L”
R1232Dxx1A, MODE=”H”
∗
1
∗
1
V
OUT
V
FB1
V
FB2
∆V
OUT
/∆Topt
fosc
I
DD1
I
DD2
Istandby
I
LXleak
R
ONP
R
ONN
Maxduty
ton
tstart
tprot
I
LX
limit
V
UVLO1
V
UVLO2
I
CE
I
VFB
I
MODE
V
CEH
V
CEL
V
MODEH
V
MODEL
×0.980
×0.975
0.784
0.780
0.800
0.800
±150
0.75
70
10
1.00
140
45
0.0
−5.0
0.0
0.20
0.20
100
40
0.5
0.1
1.0
2.10
2.20
65
1.0
2.0
1.4
2.25
V
UVLO1
+0.10
0.0
0.0
0.0
×1.020
×1.025
0.816
0.820
V
V
V
V
ppm/
°C
Feedback Voltage1 (PWM Mode) R1232D001C, MODE=”L”
Feedback Voltage2 (VFM Mode) R1232D001C, MODE=”H”
Step-down Output Voltage
Temperature Coefficient
Oscillator Frequency (A/C)
Supply Current1 (A/C)
Supply Current2 (A/C)
Standby Current
L
X
Leakage Current
−40°C
<
=
<
=
Topt
85°C
1MHz type V
IN
=5.0V
PWM mode
∗
2
, V
FB
=”H”
VFM mode
∗
3
, V
FB
=”H”
∗
1
V
CE
=0V,MODE=”L”
V
IN
=5.5V,
V
CE
=0V,
V
LX
=0V/5.5V
1.25
190
80
5.0
5.0
0.35
0.35
90
1.4
10.0
2.40
2.50
0.1
0.1
0.1
0.3
MHz
µA
µA
µA
µA
Ω
Ω
%
%
ms
ms
A
V
V
µA
µA
µA
V
V
V
V
ON Resistance of Pch Transistor V
IN
=5.0V,
I
LX
=200mA
ON Resistance of Nch Transistor V
IN
=5.0V,
I
LX
=200mA
Oscillator Maximum Duty Cycle
VFM On Duty
Soft-start Time (A/C)
Protection Delay Time
LX Current Limit
UVLO Detector Threshold
UVLO Released Voltage
CE Input Current
VFB Input Current
Mode Input Current
CE "H" Input Voltage
CE "L" Input Voltage
MODE "H" Input Voltage
MODE "L" Input Voltage
V
IN
=5.5V,
V
DD
=5.5V
V
IN
=5.5V,
V
DD
=5.5V
V
IN
=5.5V,
V
DD
=5.5V
V
IN
=V
DD
=5.5V
V
IN
=V
DD
=3.0V
V
IN
=V
DD
=5.5V
V
IN
=V
DD
=3.0V
1.5
V
MODE
=0V
V
IN
=5.0V,
VFM Mode
V
IN
=5.0V
V
IN
=5.0V
V
IN
=5.0V
−0.1
−0.1
−0.1
1.5
0.3
∗1
At VFM mode, Synchronous rectifier Nch driver is always off, therefore, an external shottky diode is
necessary.
∗2
V
FB
=GND
∗3
V
FB
>V
IN
/ internal oscillator is halted.
5
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