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Preliminary
RT9261B
VFM Step-Up DC/DC Converter
General Description
The RT9261B Series are VFM Step-up DC/DC converter ICs with ultra low supply current by CMOS process and suitable for use with battery-powered instruments. The RT9261B 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 with the RT9261B IC and only three external components. The EN pin enables the circuit to set the standby supply current at a maximum of 0.5A.
Features
Minimal Number of External Components (Only an Inductor, a Diode, and a Capacitor) Ultra Low Input Current (6.5A at Switch Off) Capable of Supplying 50mA Output Current with Internal Switch 2% Output Voltage Accuracy Low Ripple and Low Noise Low Start-up Voltage, 0.8V at 1mA 80% 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
Ordering Information
RT9261BPackage Type B : SOT-23-5 X : SOT-89 Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard) Output Voltage 15 : 1.5V 16 : 1.6V : 49 : 4.9V 50 : 5.0V
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 appliances, which require higher voltage than that of batteries used in the appliances
Pin Configurations
(TOP VIEW)
EN 1 2 3 4 GND 5 LX
Note : RichTek Pb-free and Green products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100% matte tin (Sn) plating.
NC VOUT
SOT-23-5
Marking Information
For marking information, contact our sales representative directly or through a RichTek distributor located in your area, otherwise visit our website for detail.
1 2 3
GND VOUT (TAB)
LX
SOT-89
DS9261B-12 March 2007
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RT9261B
Typical Application Circuit
Preliminary
D1 1N5819 L1 RT9261B LX VOUT GND VOUT
+
VIN
COUT 22uF
D1 1N5819 L1 LX VIN EN RT9261B VOUT GND VOUT COUT 22uF
+
* L1 ranges from 27H to 120H
Functional Pin Description
Pin No. -xxCX 1 2 3 ---xxCB 4 2 5 1 3 GND VOUT LX EN NC Ground Output Voltage Pin for Switching Chip Enable (Active High) No Connection Pin Name Pin Function
Function Block Diagram
LX
LXSW
VLX Limiter VREF Buffer
+
Error Amplifier
VOUT
GND OSC 190kHz
Chip Enable
EN
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DS9261B-12 March 2007
Preliminary Absolute Maximum Ratings
Output Voltage -------------------------------------------------------------------------------------------------------LX Pin Voltage --------------------------------------------------------------------------------------------------------EN Pin Voltage(1) -----------------------------------------------------------------------------------------------------LX Pin Output Current ----------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25C SOT-89 -----------------------------------------------------------------------------------------------------------------SOT-23-5 --------------------------------------------------------------------------------------------------------------Package Thermal Resistance SOT-89, JC -----------------------------------------------------------------------------------------------------------SOT-89, JA -----------------------------------------------------------------------------------------------------------SOT-23-5, JA ---------------------------------------------------------------------------------------------------------Operating Temperature Range ------------------------------------------------------------------------------------Storage Temperature Range --------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------Notes: (1) Applicable to RT9261B-xxCB
RT9261B
8V 8V
-0.3 to VOUT +0.3V
400mA 0.5W 0.25W 100 C/W 300 C/W 250 C/W -20 to +85C -65C to 150C 260C
Electrical Characteristics
Parameter Output Voltage Accuracy Input Voltage Start-up Voltage Hold-on Voltage Input Current 1
(1) (2)
(Refer to Figure 1)
Symbol VOUT VIN VST VHO IOUT = 1mA, VIN: 0 2V IOUT = 1mA, VIN: 2 0V To be measured at VIN in continuous switching To be measured at VOUT in switch off condition Test Conditions Min -2 --0.7 -----120 160 -140 140 65 -LX switch on 0.65 Typ --0.8 -24 36 6.5 18 20 ---190 190 75 80 0.8 Max Units +2 7 1 -36 45 10 36 45 --0.5 240 320 85 -1.0 mA A kHz kHz % % V % V V V A A
VOUT 3.5V
(1) (2)
3.5V < VOUT 5V
Input Current 2
Input Current 3
VOUT 3.5V
(1)
3.5V < VOUT 5V LX Switching Current LX Leakage Current Maximum Oscillator Frequency Oscillator Duty Cycle Efficiency VLX Voltage Limit
Notes:
(2)
To be measured at VIN in no load (guaranteed by I1 and I2) ISWITCHING VLX = 0.4V ILEAKAGE FMAX DOSC VLX = 6V VOUT = 2.5V to 5V VOUT = 1.5V to 2.4V On (VLX "L") side
A
VOUT 3.5V
(1) (2)
3.5V < VOUT 5V
(1) VIN = 1.8V, VSS = 0V, IOUT = 1mA, Topt = 25 C, and use External Circuit of Typical Application (2) VIN = 3V, VSS = 0V, IOUT = 1mA, Topt= 25C, and External Circuit of Typical Application DS9261B-12 March 2007 www.richtek.com 3
RT9261B
Electrical Characteristics
Parameter Output Voltage Accuracy Input Voltage Start-up Voltage Hold-on Voltage Efficiency Input Current 1 Input Current 2 Input Current 3
(1) (2)
Preliminary
(Refer to Figure 2)
Symbol VOUT VIN VST VHO VOUT 3.5V
(1) (2)
Test Conditions
Min -2 --
Typ --0.8 -80 24 36 6.5 18 20 -------190 190 75 0.8
Max Units +2 7 1 --36 45 10 36 45 --0.5 -0.2 0.5 -240 320 85 1.0 % V V V % A A A
IOUT = 1mA, VIN: 0 2V IOUT = 1mA, VIN: 2 0V
-0.7 --
3.5V < VOUT 5V
To be measured at VIN in continuous switching To be measured at VOUT in switch off condition
-----120 160 -0.4xVOUT ---0.5 140 140 65 0.65
VOUT 3.5V VOUT 3.5V
(1) (2)
3.5V < VOUT 5V
(1)
To be measured at VIN in no load (guaranteed by I1 and I2) ISWITCHING VLX = 0.4V ILEAKAGE VLX = 6V VIN = VOUT * 0.9 VIN = VOUT * 0.9 EN = VOUT EN = 0V FMAX DOSC VOUT = 2.5V to 5V VOUT = 1.5V to 2.4V On (VLX "L") side LX switch on
LX Switching Current LX Leakage Current EN "H" Level EN "L" Level EN "H" Input Current EN " L" Input Current
3.5V < VOUT 5V
(2)
mA A V V A A kHz kHz % V
Maximum Oscillator Frequency Oscillator Duty Cycle VLX Voltage Limit
Notes:
(1) VIN = 1.8V, VSS = 0V, IOUT = 1mA, Topt = 25C, and use External Circuit of Typical Application (2) VIN = 3V, VSS = 0V, IOUT = 1mA, Topt= 25C, and External Circuit of Typical Application
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DS9261B-12 March 2007
Preliminary Typical Operating Characteristics
Start-up/Hold-on Voltage Vstart/Vhold (V)1
RT9261B
Output Voltage vs. Output Current
4.0 3.5
Start-up/Hold-on Voltage vs. Output Current
2.5
Output Voltage (V) 1
2
3.0V 2.5V 1.0V 1.5V 2.0V
3.0 2.5 2.0 1.5 1.0 0.5 0.0
1.5
Vstart
1
0.5
Vhold VOUT = 3.3V L = 47uH
VOUT = 3.3V
0 50 100 150 200
0 0 30 60 90 120 150 180
Output Current (mA)
Output Current (mA)
Output Current vs. Ripple Voltage
300
Output Current vs. Ripple Voltage
90
2.5V
80
3.0V
Ripple Voltage (mVp-p) 1
2.0V 3.0V
Ripple Voltage (mVp-p)1
250 200 150 100 50
70 60 50 40 30 20 10 0
2.0V 2.5V
1.5V VOUT = 3.3V COUT = 20uF L = 47uH
100 150 200
1.5V 1.0V
0 50 100
1.0V
0 0 50
VOUT = 3.3V COUT = 68uF L = 47uH
150 200
Output Current (mA)
Output Current (mA)
Output Current vs. Ripple Voltage
25
90 80
Efficiency vs. output Current
3.0V 2.5V 1.0V 1.5V 2.0V
Ripple Voltage (mVp-p)1
20
2.5V
70
Efficiency (%)1
60 50 40 30 20 10 0
15
3.0V
10
1.0V VOUT = 3.3V COUT = 170uF L = 47uH
100 150 200
5
0 0
2.0V 1.5V
50
VOUT = 3.3V
0 50 100 150 200
Output Current (mA)
DS9261B-12 March 2007
Output Current (mA)
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RT9261B
Start-up/Hold-on Voltage Vstart/Vhold (V)1
Preliminary
Start-up/Hold-on Voltage vs. Output Current
2.5
4.0 3.5
Output Voltage vs. Output Current
3.0V 1.5V 1.0V 2.0V 2.5V
Output Voltage (V) 1
2
3.0 2.5 2.0 1.5 1.0 0.5 0.0
1.5
Vstart
1
0.5
Vhold VOUT = 3.3V
VOUT = 3.3V
0 50 100 150 200
0 0 20 40 60 80 100 120
Output Current (mA)
Output Current (mA)
Output Current vs. Ripple Voltage
300
90
Output Current vs. Ripple Voltage
80
2.0V
3.0V
2.5V
Ripple Voltage (mVp-p) 1
250 200 150 100 50
Ripple Voltage (mVp-p) 1
70 60 50 40 30 20 10 0
2.5V
3.0V
2.0V 1.0V 1.5V
0 50 100
1.5V
0 0
1.0V
50 100
VOUT = 3.3V COUT = 20uF L = 100uH
150 200
VOUT = 3.3V COUT = 68uF L = 100uH
150 200
Output Current (mA)
Output Current (mA)
Output Current vs. Ripple Voltage
18 16
Efficiency vs. output Current
100 90
2.5V 3.0V 2.0V
3.0V 1.0V 1.5V 2.0V 2.5V
Ripple Voltage (mVp-p) 1
14 12 10 8 6 4 2 0 0
80
Efficiency (%) 1
VOUT = 3.3V COUT = 170uF L = 100uH
100 150 200
70 60 50 40 30 20 10 0 0
1.0V
1.5V
50
VOUT = 3.3V
50 100 150 200
Output Current (mA)
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Output Current (mA)
DS9261B-12 March 2007
Preliminary Outline Dimension
RT9261B
H D L C B
b A A1 e
Symbol A A1 B b C D e H L
Dimensions In Millimeters Min 0.889 0.000 1.397 0.356 2.591 2.692 0.838 0.080 0.300 Max 1.295 0.152 1.803 0.559 2.997 3.099 1.041 0.254 0.610
Dimensions In Inches Min 0.035 0.000 0.055 0.014 0.102 0.106 0.033 0.003 0.012 Max 0.051 0.006 0.071 0.022 0.118 0.122 0.041 0.010 0.024
SOT-23-5 Surface Mount Package
DS9261B-12 March 2007
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RT9261B
Preliminary
D D1
A
C
B
C1 e e H A b b
Dimensions In Inches Min 0.055 0.014 0.094 0.016 0.155 0.031 0.173 0.055 0.057 0.014 Max 0.063 0.019 0.102 0.021 0.167 0.047 0.181 0.069 0.061 0.017
b1
Symbol A b B b1 C C1 D D1 e H
Dimensions In Millimeters Min 1.397 0.356 2.388 0.406 3.937 0.787 4.394 1.397 1.448 0.356 Max 1.600 0.483 2.591 0.533 4.242 1.194 4.597 1.753 1.549 0.432
3-Lead SOT-89 Surface Mount
Richtek Technology Corporation
Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
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