RT9261/A
VFM Step-Up DC/DC Converter
General Description
The RT9261 Series are VFM Step-up DC/DC ICs with ultra
low supply current by CMOS process and suitable for
use with battery-powered instruments.
The RT9261 IC consists of an oscillator, a VFM control
circuit, a driver transistor (LX switch), a reference voltage
unit, an error amplifier, resistors for voltage detection, and
a LX switch protection circuit. A low ripple and high
efficiency step-up DC/DC converter can be constructed of
this RT9261 IC with only three external components.
The RT9261A IC provides with a drive pin (EXT) for an
external transistor, so that a power transistor can be
externally applied. Therefore, the RT9261A IC is
recommended for applications where large currents are
required. EN pin enables circuit to set the standby supply
current at a maximum of 0.5μA.
Features
Minimal Number of External Components ( Only
an Inductor, a Diode, and a Capacitor)
Ultra Low Input Current ( 5μA at Switch Off)
μ
±
2% High Output Voltage Accuracy
Low Ripple and Low Noise
Low Start-up Voltage, 0.85V at 1mA
75% Efficiency with Low Cost Inductor
+50 ppm/
°
C Low Temperature-Drift
SOT-89 and SOT-23-5 Small Packages
RoHS Compliant and 100% Lead (Pb)-Free
Applications
Power source for battery-powered equipment
Power source for cameras, camcorders, VCRs, PDAs,
pagers, electronic data banks, and hand-held
communication equipment
Power source for applications, which require higher
voltage than that of batteries used in the appliances
Ordering Information
RT9261/A-
Package Type
B : SOT-23-5
X : SOT-89
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Output Voltage
15 : 1.5V
16 : 1.6V
:
49 : 4.9V
50 : 5.0V
Use external switch
Use internal switch
Note :
Richtek products are :
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Pin Configurations
(TOP VIEW)
1
2
3
1
2
3
GND VOUT
(TAB)
LX
GND VOUT EXT
(TAB)
RT9261
SOT-89
LX
5
RT9261A
GND
4
EXT
5
GND
4
2
3
2
3
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
DS9261/A-16 April 2011
EN VOUT NC
EN VOUT NC
RT9261
SOT-23-5
RT9261A
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1
RT9261/A
Absolute Maximum Ratings
Output Voltage ------------------------------------------------------------------------------------------------------ 8V
LX Pin Voltage
(1)
------------------------------------------------------------------------------------
8V
EXT Pin Voltage
(2)
-------------------------------------------------------------------------------------------------
−
0.3 to V
OUT
+0.3V
EN Pin Voltage
(3)
---------------------------------------------------------------------------------------------------
−
0.3 to V
OUT
+0.3V
LX Pin Output Current
(1)
------------------------------------------------------------------------------------------ 250mA
EXT Pin Current
(2)
--------------------------------------------------------------------------------------------------
±50mA
Power Dissipation, P
D
@ T
A
= 25°C
SOT-89 ---------------------------------------------------------------------------------------------------------------- 0.5W
SOT-23-5 -------------------------------------------------------------------------------------------------------------- 0.25W
Package Thermal Resistance
SOT-89,
θ
JC
----------------------------------------------------------------------------------------------------------
SOT-89,
θ
JA
----------------------------------------------------------------------------------------------------------
SOT-23-5,
θ
JA
--------------------------------------------------------------------------------------------------------
Operating Temperature Range -----------------------------------------------------------------------------------
100°C/W
300°C/W
250°C/W
−
20 to +85°C
Storage Temperature Range -------------------------------------------------------------------------------------- 165°C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°C
Notes:
(1) Applicable to RT9261-
xX and RT9261-
xB
(2) Applicable to RT9261A-
xX and RT9261A-
xB
(3) Applicable to RT9261-
xB and RT9261A-
xB
Electrical Characteristics
(Refer to Figure 1)
Parameter
Output Voltage Accuracy
Input Voltage
Start-up Voltage
Hold-on Voltage
Input Current 1
Input Current 2
LX Switching Current
LX Leakage Current
Maximum Oscillator
Oscillator Duty Cycle
Efficiency
V
LX
Voltage Limit
Notes:
(1)Unless otherwise provided, V
IN
= 1.8V, V
SS
= 0V, I
OUT
= 10mA, T
OPT
= 25°C, and External Circuit of Typical Application
(2)Unless otherwise provided, V
IN
= 3V, V
SS
= 0V, I
OUT
= 10mA, T
OPT
= 25°C, and External Circuit of Typical Application
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DS9261/A-16 April 2011
Symbol
ΔV
OUT
V
IN
V
ST
V
HO
Test Conditions
Min
−2
--
Typ
--
--
0.85
--
15
18
5
--
--
--
120
75
70
75
0.8
Max
2
7
1
--
18
24
8
--
--
0.5
160
85
80
--
1
Unit
%
V
V
V
μA
μA
mA
μA
kHz
%
%
%
V
I
OUT
= 1mA, V
IN
: 0
→
2V
I
OUT
= 1mA, V
IN
: 2
→
0V
V
OUT
≤
3.5V
(1)
V
IN
at no load
3.5V
<
V
OUT
≤
5V
(2)
V
OUT
in switch off condition
--
0.7
--
--
--
(1)
(2)
I
SWITCHING
I
LEAKAGE
F
MAX
D
OSC
V
LX
= 0.4V
V
LX
= 6V
V
OUT
≤
3.5V
60
80
--
80
3.5V
<
V
OUT
≤
5V
On ( V
LX
” L ” ) side
V
OUT
= 2.5V to 5V
V
OUT
= 1.5V to 2.4V
65
60
--
0.65
L
X
switch on
RT9261/A
Electrical Characteristics
(Refer to Figure 2)
Parameter
Output Voltage Accuracy
Input Voltage
Start-up Voltage
Input Current 1
Input Current 2
EXT “H” Output Current
EXT “L” Output Current
Maximum Oscillator Frequency
Oscillator Duty Cycle
Notes:
(1)Unless otherwise provided, V
IN
= 1.8V, V
SS
= 0V, I
OUT
= 10mA, T
OPT
= 25° C, and use External Circuit of Typical
Application
(2)Unless otherwise provided, V
IN
= 3V, V
SS
= 0V, I
OUT
= 10mA, T
OPT
= 25° C, and External Circuit of Typical Application
Symbol
ΔV
OUT
V
IN
V
ST
Test Conditions
Min
−2
--
Typ
--
--
0.85
30
60
6
--
--
--
--
120
75
70
Max
+2
7
1.0
50
90
10
--
--
--
--
160
85
80
Unit
%
V
V
μA
μA
mA
mA
kHz
%
%
I
OUT
= 1mA, V
IN
: 0
→
2V
(1)
V
OUT
≤
3.5V
V
IN
at no load
3.5V
<
V
OUT
≤
5V
(2)
V
OUT
≤
3.5V
(1)
V
OUT
in switch off
condition
3.5V
<
V
OUT
≤
5V
(2)
V
OUT
≤
3.5V
V
EXT
= V
OUT
– 0.4V
(2)
3.5V
<
V
OUT
≤
5V
(1)
V
OUT
≤
3.5V
V
EXT
= 0.4V
(2)
3.5V
<
V
OUT
≤
5V
(1)
--
--
--
--
−1.5
−2
1.5
2
80
65
60
F
MAX
D
OSC
V
EXT
” H ” side
V
OUT
= 2.5V to 5V
V
OUT
= 1.5V to 2.4V
DS9261/A-16 April 2011
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