RN5RK SERIES
VFM STEP-UP DC/DC CONVERTER
NO.EA-045-080411
OUTLINE
The RN5RKxx1A/xx1B/xx2A Series are CMOS-based VFM (Chopper) Step-up DC/DC converter ICs with ultra
low supply current and high output voltage accuracy.
Each of the RN5RKxx1A/xx1B consists of an oscillator, a VFM control circuit, a driver transistor to have low
ON resistance (Lx switch), a reference voltage unit, a high speed comparator, resistors for voltage detection, an
Lx switch protection circuit and an internal chip enable circuit. A low ripple, high efficiency step-up DC/DC
converter can be composed of this RN5RKxx1A/xx1B with only three external components: an inductor, a diode
and a capacitor.
The RN5RKxx2A uses the same chip as what is employed in the RN5RKxx1A/1B IC and has a drive pin (EXT)
for an external transistor instead of an Lx pin. As it is possible to load a large output current with a power
transistor which has a low saturation voltage, RN5RKxx2A IC is recommendable to users who need an output
current as large as between several tens mA and several hundreds mA.
Using the chip enable function, it is possible to make the supply current on standby minimized.
Since the package for these ICs is SOT-23-5, high density mounting of the ICs on board is possible.
FEATURES
•
Small Number of External Components .............................. Only an inductor, a diode and a capacitor
(RN5RKxx1A/xx1B)
•
Standby Current ................................................................... Typ. 0µA
•
Low Temperature-Drift Coefficient of Output Voltage........... Typ.
±100ppm/°C
•
Output Voltage Range.......................................................... 2.0V to 5.5V
•
Two Kinds of Duty Ratio....................................................... 77% (xx1A, xx2A)/ 55% (xx1B)
•
High Output Voltage Accuracy .............................................
±2.5%
•
Small Packages ................................................................. SOT-23-5
•
High Efficiency ..................................................................... Typ. 85% (RN5RK301B, V
IN
=2V, I
OUT
=10mA)
•
Low Ripple and Low Noise
•
Including a Driver Transistor with Low ON Resistance........ Only RN5RKxx1A/xx1B
•
Low Start-up Voltage............................................................ Max.0.9V
APPLICATIONS
•
Power source for battery-powered equipment.
•
Power source for cameras, camcorders, VCRs, and hand-held communication equipment.
•
Power source for those appliances which require higher cell voltage than that of batteries.
1
RN5RK
OUTLINE DIAGRAM
RN5RKxx1x
Vref
RN5RKxx2A
Vref
Lx 5
LxSW
V
LX
limiter
Buffer
−
VFM Control
OSC 100kHz
Chip Enable
＋
Error Amp.
2 V
OUT
EXT 5
Buffer
−
VFM Control
＋
OSC 100kHz Error Amp.
Chip Enable
2 V
OUT
4 GND
1
CE
1
CE
4 GND
SELECTION GUIDE
The output voltage, the driver type, the duty cycle 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:
RN5RKxxxx-xx
↑ ↑↑ ↑
a bc d
Code
a
←Part
Number
Contents
Setting Output Voltage (V
OUT
) :
Stepwise setting with a step of 0.1V in the range of 2.0V to 5.5V is possible.
Designation of Driver
1: Internal Lx Tr. Driver
2: External Tr. Driver
Designation of Duty Cycle
A: 77%
B: 55%
Designation of Taping type
Ex. TR (Refer to Taping Specifications; TR type is the standard direction.)
b
c
d
2
RN5RK
ABSOLUTE MAXIMUM RATINGS
•
RN5RKxx1x
Symbol
V
OUT
V
LX
V
CE
I
LX
P
D
Topt
Tstg
Item
Step-up Output Pin Voltage
Lx Pin Voltage
CE Pin Voltage
Lx Pin Output Current
Power Dissipation (SOT-23-5)*
Operating Temperature Range
Storage Temperature Range
Rating
‐0.3
to 9.0
‐0.3
to 9.0
‐0.3
to V
OUT
+0.3
500
420
‐40
to 85
‐55
to 125
Unit
V
V
V
mA
mW
°C
°C
•
RN5RKxx2A
Symbol
V
OUT
V
EXT
V
CE
I
EXT
P
D
Topt
Tstg
Item
Step-up Output Pin Voltage
EXT Pin Voltage
CE Pin Voltage
EXT Pin Output Current
Power Dissipation (SOT-23-5)*
1
Operating Temperature Range
Storage Temperature Range
Rating
‐0.3
to 9.0
‐0.3
to V
OUT
+0.3
‐0.3
to V
OUT
+0.3
±30
420
‐40
to 85
‐55
to 125
Unit
V
V
V
mA
mW
°C
°C
*)For Power Dissipation, please refer to PACKAGE INFORMATION to be described.
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum ratings are threshold limit values that must not be exceeded even for an instant under any
conditions. Moreover, such values for any two items must not be reached simultaneously. Operation above
these absolute maximum ratings may cause degradation or permanent damage to the device. These are stress
ratings only and do not necessarily imply functional operation below these limits.
4
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