RN5RK SERIES
VFM STEP-UP DC/DC CONVERTER
NO.EA-045-111124
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 and the duty cycle for the ICs can be selected at the user's request.
Product Name
RN5RKxx∗$-TR-FE
Package
SOT-23-5
Quantity per Reel
3,000 pcs
Pb Free
○
Halogen Free
○
xx：The output voltage can be designed in the range from 2.0V(20) to 5.5V(55) in 0.1V steps.
∗
：Designation
of Driver
（1）Internal
Lx Tr. Driver
（2）External
Tr. Driver
$
：Designation
of Duty Cycle
（A）77％
（B）55％
2
RN5RK
PIN CONFIGURATIONS
•
5
SOT-23-5
4
(mark side)
1
2
3
PIN DISCRIPTION
•
RN5RKxx1x
Pin No.
1
2
3
4
5
Symbol
CE
V
OUT
NC
GND
L
X
Description
Chip Enable Pin
Step-up Output Monitoring Pin,
Power Supply (for device itself)
No Connection
Ground Pin
Switching Pin
(Nch Open Drain)
•
RN5RKxx2A
Pin No.
1
2
3
4
5
Symbol
CE
V
OUT
NC
GND
EXT
Description
Chip Enable Pin
Step-up Output Monitoring Pin,
Power Supply (for device itself)
No Connection
Ground Pin
External Tr. Drive Pin
(CMOS Output)
3
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.
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.
4
RN5RK
ELECTRICAL CHARACTERISTICS
•
RN5RKxx1A/xx1B
Symbol
V
OUT
V
IN
ΔV
OUT
/
ΔT
opt
Vstart
ΔVstart/
ΔT
opt
Vhold
Vhold
I
DD2
I
standby
I
LXleak
fosc
Δfosc/
ΔT
opt
Maxduty
V
LXlim
V
CEH
V
CEL
I
CEH
I
CEL
Item
Output Voltage
Input Voltage
Output Voltage
Temperature Coefficient
Start-Up Voltage
Start-Up Voltage
Temperature Coefficient
Hold-on Voltage (xx1A)
Hold-on Voltage (xx1B)
Supply Current2
Standby Current
Lx Leakage Current
Maximum Oscillator
Frequency
Frequency Temperature
Coefficient
−40°C
<
=
Topt=25°C
Conditions
V
IN
=Set
V
OUT
×0.6,
I
OUT
=1mA
Min.
×0.975
Typ.
Max.
×1.025
8.0
Unit
V
V
ppm
/°C
T
opt
<
=
85°C
±100
0.75
-1.6
0.7
0.9
2
5
0.5
1
80
100
0.41
70
47
0.4
0.9
0.3
-0.5
-0.5
0
0
25
30
35
40
45
50
55
0.5
0.5
50
55
60
65
75
80
90
77
55
0.6
85
63
0.8
120
0.90
V
IN
=0V→2V*
1
-40°C
<
T
opt
<
85°C
=
=
1
V
IN
=0V→2V*
V
IN
=2V→0V*
1
V
IN
=2V→0V*
1
V
OUT
=V
CE
=Set V
OUT
+0.5V
V
OUT
=6V,
V
CE
=0V
V
OUT
=V
LX
=8V
V
OUT
=V
CE
=Set V
OUT
×0.96
-40°C
<
=
V
mV/
°C
V
V
μA
μA
μA
kHz
kHz/
°C
%
%
V
V
V
μA
μA
μA
T
opt
<
=
85°C
Oscillator Duty Cycle (xx1A) V
OUT
=V
CE
=Set
V
OUT
×0.96,
Oscillator Duty Cycle (xx1B) ON (V
LX
"L" side)
V
LX
Voltage Limit
CE "H" Input Voltage
CE "L" Input Voltage
CE "H" Input Current
CE "L" Input Current
V
OUT
=V
CE
=1.95V, Lx Switch ON
V
OUT
=V
CE
=Set V
OUT
×0.96,
Judgment is made by the Lx
waveform
V
OUT
=6.0V,
V
CE
=6.0V
V
OUT
=6.0V,
V
CE
=0V
2.0V
2.5V
3.0V
Supply Current1 *
2
<
=
<
=
<
=
<
=
<
=
<
=
<
=
Set V
OUT
Set V
OUT
Set V
OUT
Set V
OUT
Set V
OUT
Set V
OUT
Set V
OUT
<
=
<
=
<
=
<
=
<
=
<
=
<
=
2.4V
2.9V
3.4V
3.9V
4.4V
4.9V
5.5V
I
DD1
3.5V
4.0V
4.5V
5.0V
μA
5
