Preliminary RT9261/A
DS9261/A-03 January 2002 www.richtek-ic.com.tw
1
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. CE pin enables circuit to set the
standby supply current at a maximum of 0.5µA.
Ordering Information
RT9261A-
Features
z Minimal Number of External Components ( Only
an inductor, a diode, and a capacitor)
z Ultra Low Input Current ( 5µ
µµ
µA at Switch Off)
z ±
±±
± 2% High Output Voltage Accuracy
z Low Ripple and Low Noise
z Low Start-up Voltage, 0.85V at 1mA
z 75% Efficiency with Low Cost Inductor
z +50 ppm/°
°°
°C Low Temperature-Drift
z SOT-89 and SOT-25 Small Packages
Applications
z Power source for battery-powered equipment
z Power source for cameras, camcorders, VCRs,
PDAs, pagers, electronic data banks, and hand-
held communication equipment
z Power source for applications, which require
higher voltage than that of batteries used in the
appliances
Pin Configurations
Part Number Pin Configurations
RT9261-CX
(Plastic SOT-89)
TOP VIEW
1. GND
2. VOUT (TAB)
3. LX
RT9261A-CX
(Plastic SOT-89)
TOP VIEW
1. GND
2. VOUT (TAB)
3. EXT
RT9261-CB
(Plastic SOT-25)
TOP VIEW
1. CE
2. VOUT
3. NC
4. GND
5. LX
RT9261A-CB
(Plastic SOT-25)
TOP VIEW
1. CE
2. VOUT
3. NC
4. GND
5. EXT
Operating temperature range
C: Commercial standard
Package type
B : SOT-25
X : SOT-89
Output voltage
15 : 1.5V
16 : 1.6V
:
49 : 4.9V
50 : 5.0V
A : Use external switch
Use internal switch
123
123
54
321
54
321
RT9261/A Preliminary
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Absolute Maximum Ratings
z Output Voltage 8V
z LX Pin Voltage (1) 8V
z EXT Pin Voltage (2) -0.3 to VOUT +0.3V
z CE Pin Voltage (3) -0.3 to VOUT +0.3V
z LX Pin Output Current (1) 250mA
z EXT Pin Current(2) ±50mA
z Power Dissipation, PD @ TA = 25°C
z SOT-89 0.5W
SOT-25 0.25W
z Package Thermal Resistance
SOT-89, θJC 100°C/W
SOT-89, θJA 300°C/W
SOT-25, θJA 250°C/W
z Operating Temperature Range -20 to +85°C
z Storage Temperature Range 165°C
z Lead Temperature (Soldering, 10 sec.) 260°C
Notes:
(1) Applicable to RT9261-CX and RT9261-CB
(2) Applicable to RT9261A-CX and RT9261A-CB
(3) Applicable to RT9261-CB and RT9261A-CB
Electrical Characteristics (Refer to Fig. 1)
Parameter Symbol Test Conditions Min Typ Max Units
Output Voltage Accuracy ∆VOUT -2 -- +2 %
Input Voltage VIN -- -- 7 V
Start-up Voltage VST IOUT = 1mA, VIN: 0 → 2V -- 0.85 1.0 V
Hold-on Voltage VHO IOUT = 1mA, VIN: 2 → 0V 0.7 -- -- V
VOUT ≤ 3.5V (1) -- 15 18
Input Current 1
3.5V < VOUT ≤ 5V (2)
To be measured at VIN at
no load -- 18 24 µA
Input Current 2 To be measured at VOUT
in switch off condition -- 5 8 µA
VOUT ≤ 3.5V (1) 60 -- --
LX Switching Current
3.5V < VOUT ≤ 5V (2) ISWITCHING VLX = 0.4V 80 -- -- mA
LX Leakage Current ILEAKAGE VLX = 6V -- -- 0.5 µA
Maximum Oscillator FMAX 80 120 160 KHz
Oscillator Duty Cycle DOSC On ( VLX ” L ” ) side 65 75 85 %
Efficiency -- 75 -- %
VLX Voltage Limit LX switch on 0.65 0.8 1.0 V
Notes:
(1) VIN = 1.8V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and External Circuit of Typical Application
(2) VIN = 3V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and External Circuit of Typical Application
Preliminary RT9261/A
DS9261/A-03 January 2002 www.richtek-ic.com.tw
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Electrical Characteristics (Refer to Fig. 2)
Parameter Symbol Test Conditions Min Typ Max Units
Output Voltage Accuracy ∆VOUT -2 -- +2 %
Input Voltage VIN -- -- 7 V
Start-up Voltage VST IOUT = 1mA, VIN : 0 → 2V -- 0.85 1.0 V
VOUT ≤ 3.5V (1) -- 30 50
Input Current 1
3.5V < VOUT ≤ 5V (2)
To be measured at VIN at no
load -- 60 90 µA
VOUT ≤ 3.5V (1)
Input Current 2
3.5V < VOUT ≤ 5V (2)
To be measured at VOUT in
switch off condition -- 6 10 µA
VOUT ≤ 3.5V (1) -1.5 -- --
EXT “H” Output
Current 3.5V < VOUT ≤ 5V (2) VEXT = VOUT – 0.4V -2 -- -- mA
VOUT ≤ 3.5V (1) 1.5 -- --
EXT “L” Output
Current 3.5V < VOUT ≤ 5V (2) VEXT = 0.4V 2----
mA
Maximum Oscillator Frequency FMAX 80 120 160 KHz
Oscillator Duty Cycle DOSC VEXT ” H ” side 65 75 85 %
Notes:
(1) Unless otherwise provided, VIN = 1.8V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and use External Circuit of
Typical Application
(2) Unless otherwise provided, VIN = 3V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and External Circuit of Typical
Application
RT9261/A Preliminary
www.richtek-ic.com.tw DS9261/A-03 January 2002
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Electrical Characteristics (Refer to Fig. 3)
Parameter Symbol Test Conditions Min Typ Max Units
Output Voltage Accuracy ∆VOUT -2 -- +2 %
Input Voltage VIN -- -- 7 V
Start-up Voltage VST IOUT = 1mA, VIN : 0 → 2V -- 0.85 1.0 V
Hold-on Voltage VHO IOUT = 1mA, VIN : 2 → 0V 0.7 -- -- V
VOUT ≤ 3.5V (1) -- 75 --
Efficiency
3.5V < VOUT ≤ 5V (2) -- 85 -- %
VOUT ≤ 3.5V (1) -- 15 18
Input Current 1
3.5V < VOUT ≤ 5V (2)
To be measured at VIN at
no load -- 18 24 µA
VOUT ≤ 3.5V (1) -- 5 8
Input Current 2
3.5V < VOUT ≤ 5V (2)
To be measured at VOUT
in switch off condition -- 6 10 µA
VOUT ≤ 3.5V (1) 60 -- --
LX Switching
Current 3.5V < VOUT ≤ 5V (2) ISWITCHING VLX = 0.4V 80 -- -- mA
LX Leakage Current ILEAKAGE VLX = 6V -- -- 0.5 µA
CE “H” Level VIN = VOUT × 0.9 0.4× VOUT -- -- V
CE “ L” Level VIN = VOUT × 0.9 -- -- 0.2 V
CE “ H” Input Current CE = VOUT -- -- 0.5 µA
CE “ L“ Input Current CE = 0V -0.5 -- -- µA
Maximum Oscillator Frequency FMAX 80 120 160 KHz
Oscillator Duty Cycle DOSC On (VLX ” L” ) side 65 75 85 %
VLX Voltage Limit LX switch on 0.65 0.8 1.0 V
Notes:
(1) Unless otherwise provided, VIN = 1.8V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and use External Circuit of
Typical Application
(2) Unless otherwise provided, VIN = 3V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and External Circuit of Typical
Application
Preliminary RT9261/A
DS9261/A-03 January 2002 www.richtek-ic.com.tw
5
Electrical Characteristics (Refer to Fig. 4)
Parameter Symbol Test Conditions Min Typ Max Units
Output Voltage Accuracy ∆VOUT -2 -- +2 %
Input Voltage VIN -- -- 7 V
Start-up Voltage VST IOUT = 1mA, VIN : 0 → 2V -- 0.85 1.0 V
VOUT ≤ 3.5V (1) -- 75 --
Efficiency
3.5V < VOUT ≤ 5V (2) -- 85 -- %
VOUT ≤ 3.5V (1) -- 30 50
Input Current 1
3.5V < VOUT ≤ 5V (2)
To be measured at VIN at
no load -- 60 90 µA
VOUT ≤ 3.5V (1)
Input Current 2
3.5V < VOUT ≤ 5V (2)
To be measured at VOUT in
switch off condition -- 6 10 µA
VOUT ≤ 3.5V (1) -1.5 -- --
EXT “H” Output
Current 3.5V < VOUT ≤ 5V (2) VEXT = VOUT – 0.4V -2 -- -- mA
VOUT ≤ 3.5V (1) 1.5 -- --
EXT “L” Output
Current 3.5V < VOUT ≤ 5V (2) VEXT = 0.4V 2----
mA
CE “H” Level VIN = VOUT × 0.9 0.4× VOUT -- -- V
CE “ L” Level VIN = VOUT × 0.9 -- -- 0.2 V
CE “ H” Input Current CE = VOUT -- -- 0.5 µA
CE “ L“ Input Current CE = 0V -0.5 -- -- µA
Maximum Oscillator Frequency FMAX 80 120 160 KHz
Oscillator Duty Cycle DOSC On (VLX ” L” ) side 65 75 85 %
VLX Voltage Limit LX switch on 0.65 0.8 1.0 V
Notes:
(1) Unless otherwise provided, VIN = 1.8V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and use External Circuit of
Typical Application
(2) Unless otherwise provided, VIN = 3V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and External Circuit of Typical
Application
RT9261/A Preliminary
www.richtek-ic.com.tw DS9261/A-03 January 2002
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Function Block Diagram
Notes:
(1) LX Pin .…… only for 9261-CX and 9261-CB
(2) EXT Pin …… only for 9261A-CX and 9261A-CB
(3) CE Pin …… only for 9261-CB and 9261A-CB
Pin Description
Pin No.
-xxCX A-xxCX -xxCB A-xxCB Pin Name Pin Function
1 1 4 4 GND Ground
2 2 2 2 VOUT Output Voltage
3 -- 5 -- LX Pin for Switching
-- 3 -- 5 EXT Drive External Device
-- -- 1 1 CE Chip Enable (Active High)
-- -- 3 3 NC No Connected
VOUT
Vref
Chip Enable
OSC 100kHz
VFM Control
Buffer
VLX Limiter
Error Amp.
CE
LXSW
+
_
EXT
GND
LX
Preliminary RT9261/A
DS9261/A-03 January 2002 www.richtek-ic.com.tw
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Typical Application Circuit
Fig. 1
VOUT
Co
L1
VIN
LX VOUT
GND
D1
+
_22µF
100µH
1N5819
RT9261CX
Fig. 2
VOUT
Co
L1
VIN
EXT VOUT
GND
D1
+
_22µF
27µH1N5819
0. 01 µF
Cb
Rb
300Ω
Tr
ZTX
650
RT9261ACX
Fig. 3
VOUT
Co
L1
VIN
LX
GND
D1
+
_22µF
100µH
1N5819
EXT VOUT
CE
NC
RT9261CB
RT9261/A Preliminary
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Fig. 4
VOUT
Co
L1
VIN
EXT VOUT
GND
D1
+
_22µF
27µH1N5819
0. 01 µF
Cb
Rb
300Ω
Tr
ZTX
650
CE
LX
NC RT9261ACB
Fig. 5
VOUT
Co
L1
VIN
LX
GND
D1
+
_22µF
27µH
1N5819
EXT VOUT
CE
NC
CE
RT9261CB
Preliminary RT9261/A
DS9261/A-03 January 2002 www.richtek-ic.com.tw
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Typical Operating Charateristics
RT9261(2.7V)
Start-up/Hold-on Voltage vs. Output Current
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 1020304050
Output Current (mA)
Start-up/Hold-on Voltage Vstart/Vhold (V)
Vstart
Vhold
RT9261
VOUT = 2.7V
RT9261(2.7V)
Output Current vs. Ripple Voltage
0
20
40
60
80
100
120
0 20406080100
Output Current (mA)
Ripple Voltage (mV p-p)
0.9V
1.5V
2.0V
2.5V
RT9261
VOUT = 2.7V
RT9261(2.7V)
Output Voltage vs. Output Current
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 20406080100
Output Current (mA)
Output Voltage (V)
0.9V
1.0V 1.5V 2.0V
2.5V
RT9261
VOUT = 2.7V
Output Voltage vs. Temperature
2.60
2.65
2.70
2.75
2.80
2.85
2.90
-40 -20 0 20 40 60 80
Temperature ( C)
Output Voltage (V)
°
RT9261
VOUT = 2.7V
RT9261(2.7V)
Efficiency vs. Output Current
0
10
20
30
40
50
60
70
80
90
020406080100
Output Current (mA)
Efficiency (%)
0.9V
1.0V
1.5V
2.0V 2.5V
RT9261
VOUT = 2.7V
Supply Current vs. Temperature
0
10
20
30
40
50
60
70
-40-20 0 20406080
Temperature ( C)
Supply Current ( A)
°
Input Current 1
Input Current 2
RT9261
VOUT = 2.7V
µ
RT9261/A Preliminary
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Maximum Oscillator Frequency vs. Temp.
0
20
40
60
80
100
120
140
160
-40-20 0 20406080
Temperature ( C)
Maximum Oscillator Frequency (kHz)
°
RT9261
VOUT = 2.7V
RT9261A (2.7V)
Output Voltage vs. Output Current
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 306090120150
Output Current (mA)
Output Voltage (V)
0.9V
1.0V
1.5V 2.0V
2.5V
RT9261A
VOUT = 2.7V
Oscillator Duty Cycle vs. Temperatrue
50
60
70
80
90
100
-40 -20 0 20 40 60 80
Temperature ( C)
Oscillator Duty Cycle (%)
°
RT9261
VOUT = 2.7V
RT9261A (2.7V)
Efficiency vs. Output Current
0
10
20
30
40
50
60
70
80
0 30 60 90 120 150
Output Current (mA)
Efficiency (%)
1.0V
0.9V
1.5V
2.0V
2.5V
RT9261A
VOUT = 2.7V
Start-up/Hold-on Voltage vs. Output Current
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0306090120150
Output Current (mA)
Start-up/Hold-on Voltage Vstart/Vhold (V)
Vstart
Vhold
RT9261A
VOUT = 2.7V
RT9261A (2.7V)
Output Current vs. Ripple Voltage
0
20
40
60
80
100
120
0 30 60 90 120 150
Output Current (mA)
Ripple Voltage (mV p-p)
0.9V
1.5V
2.0V
2.5V
RT9261A
VOUT = 2.7V
Preliminary RT9261/A
DS9261/A-03 January 2002 www.richtek-ic.com.tw
11
Package Information
Dimensions In Millimeters Dimensions In Inches
Symbol Min Max Min Max
A 1.397 1.600 0.055 0.063
b 0.356 0.483 0.014 0.019
B 2.388 2.591 0.094 0.102
b1 0.406 0.533 0.016 0.021
C -- 4.242 -- 0.167
C1 0.787 1.194 0.031 0.047
D 4.394 4.597 0.173 0.181
D1 1.397 1.753 0.055 0.069
e 1.448 1.549 0.057 0.061
H 0.355 0.432 0.014 0.017
3-Lead SOT-89 Surface Mount
D
D1
C
C1
B
e e
A
bb1 b
A
H
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Dimensions In Millimeters Dimensions In Inches
Symbol Min Max Min Max
A 0.889 1.295 0.035 0.051
A1 0.000 0.152 0.000 0.006
B 1.397 1.803 0.055 0.071
b 0.356 0.559 0.014 0.022
C 2.591 2.997 0.102 0.118
D 2.692 3.099 0.106 0.122
e 0.838 1.041 0.033 0.041
H 0.102 0.254 0.004 0.010
L 0.356 0.610 0.014 0.024
SOT- 25 Surface Mount Package
b
45
B
C
D
31
L
H
A1
e
A
Preliminary RT9261/A
DS9261/A-03 January 2002 www.richtek-ic.com.tw
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RT9261/A Preliminary
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14
RICHTEK TECHNOLOGY CORP.
Headquarter
6F, No. 35, Hsintai Road, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5510047 Fax: (8863)5537749
RICHTEK TECHNOLOGY CORP.
Taipei Office (Marketing)
8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: (8862)89191466 Fax: (8862)89191465
Email: marketing@richtek-ic.com.tw
