R1240x Series
1.2 A, 30 V Step-Down DC/DC Converter
NO.EA-190-170609
OUTLINE
The R1240x is a CMOS-based Step-down DC/DC converter with internal Nch high side Tr. (0.35 Ω), which
can provide the maximum 1.2 A output current. The ICs consists of an Oscillator, a PWM control circuit, a
Reference Voltage unit, an Error amplifier, phase compensation circuits, a slope circuit, a soft-start circuit,
protection circuits, internal voltage regulators, and a switch for boot strap circuit. The ICs can make up a Step-
Down DC/DC Converter with the following external components: an inductor, resistors, a diode, and capacitors.
The R1240x is a current mode operating type DC/DC converter which does not require external current sense
resistor, and it works high speed response time, high efficiency and compatible with ceramic capacitors.
Oscillator frequency is internally set at 1.25 MHz.
As a protection function, it has cycle by cycle peak current limit function, short protection function, thermal
shutdown function and UVLO.
There are two types for short protection, A version has latch protection function with 2 ms delay time, and B
version has fold-back protection function that keep operating at short condition with lower operating frequency
and limiting the Lx current.
FEATURES
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Operating Voltage
········································· 4.5 V to 30 V
Internal Nch MOSFET Driver ····························· Typ. R
ON
= 0.35 Ω
Adjustable Output Voltage with External Resistor ··· 0.8 V to 15 V
Feedback Voltage············································ 0.8 V
±1.5%
Peak Current Limit Function ······························ Typ. 2.0 A
UVLO Function
Operating Frequency ······································· 1.25 MHz (Ver. B: 310 kHz, Fold-back Condition)
Short Protection for Output ································ Ver. A: Latch with 2 ms delay or Ver. B: Fold-back
Ceramic Capacitor Compatible
Stand-by Function ··········································· Typ. 0
µA
Package ························································ SOT-23-6W, DFN(PLP)2527-10
APPLICATIONS
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Digital Home Appliances: Digital TVs, DVD Players
OA Equipment: Printers, Fax
Hand-held Communication Equipment, Cameras, VCRs, Camcorders
Battery-powered Equipment
1
R1240x
NO.EA-190-170609
PIN DESCRIPTIONS
Top View
1
2
3
4
5
R1240K
10
9
8
7
6
10
9
8
7
6
Bottom View
1
2
3
4
5
3
4
1
2
R1240N
Top View
6
5
DFN(PLP)2527-10 Pin Configuration
SOT-23-6W Pin Configuration
R1240N001x Pin Description
Pin No.
Symbol
1
CE
2
VIN
3
Lx
4
BST
5
GND
6
VFB
R1240K003x Pin Description
Pin No.
Symbol
1
Lx
2
VIN
3
VIN
4
CE
5
TEST
6
GND
7
NC
8
VFB
9
NC
10
BST
leaving it open is also acceptable.
Description
Chip Enable Pin, Active with ”H”
Power Supply Pin
Lx Switching Pin
Bootstrap Pin
Ground Pin
Feedback Pin
Description
Lx Switching Pin
Power Supply Pin
Power Supply Pin
Chip Enable Pin, Active with ”H”
Test Pin (Open, do not connect to any line.)
Ground Pin
No Connection
Feedback Pin
No Connection
Bootstrap Pin
Tab is GND level. (They are connected to the reverse side of this IC.) The tab is better to be connected to the GND, but
3
R1240x
NO.EA-190-170609
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings
Symbol
V
IN
V
BST
V
LX
I
LX
V
CE
V
FB
Input Voltage
BST Pin Voltage
Lx Pin Voltage
Lx Pin Current
CE Pin input Voltage
VFB Pin Voltage
SOT-23-6W
P
D
Power Dissipation*
Item
Rating
−0.3
to 32
V
LX
−0.3
to V
LX
+6
−0.3
to V
IN
+0.3
2
−0.3
to V
IN
+ 0.3
−0.3
to 4
Standard Land Pattern
Standard Land Pattern
430
910
1400
°C
°C
mW
(GND = 0 V)
Unit
V
V
V
A
V
V
DFN(PLP)2527-10 High Wattage Land
Pattern
Tj
Tstg
Junction Temperature Range
Storage Temperature Range
−40
to 125
−55
to 125
∗
Refer to
Power Dissipation
for detailed information.
ABSOLUTE MAXIMUM RATINGS
Electronic and mechanical stress momentarily exceeded absolute maximum ratings may cause the permanent
damages and may degrade the life time and safety for both device and system using the device in the field.
The functional operation at or over these absolute maximum ratings is not assured.
RECOMMENDED OPERATING CONDITIONS
Recommended Operating Conditions
Symbol
V
IN
Ta
Item
Operating Input Voltage
Operating Temperature Range
Rating
4.5 to 30
−40 to 85
Unit
V
°C
RECOMMENDED OPERATING CONDITIONS
All of electronic equipment should be designed that the mounted semiconductor devices operate within the
recommended operating conditions. The semiconductor devices cannot operate normally over the recommended
operating conditions, even if when they are used over such conditions by momentary electronic noise or surge. And
the semiconductor devices may receive serious damage when they continue to operate over the recommended
operating conditions.
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Embedded System
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