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.Alow 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 0.5μA.
Features
zMinimal Number of External Components (Only an Inductor, a Diode, and a Capacitor)
zUltra Low Input Current (6.5μA at Switch Off)
zCapable of Supplying 50mA Output Current with Internal Switch
z± 2% Output Voltage Accuracy
zLow Ripple and Low Noise
zLow Start-up Voltage, 0.8V at 1mA
z80% Efficiency with Low Cost Inductor
z+50 ppm/°C Low Temperature-Drift
zSOT-89 and SOT-23-5 Small Packages
zRoHS Compliant and 100% Lead (Pb)-Free
Ordering Information
RT9261B-
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
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49 : 4.9V
50 : 5.0V
Note :
Richtek 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.
Applications
zPower source for battery-powered equipment
zPower source for cameras, camcorders, VCRs, PDAs, pagers, electronic data banks, and hand-held communication equipment
zPower source for appliances, which require higher voltage than that of batteries used in the appliances
Pin Configurations
(TOP VIEW)
LX GND
5 4
2 3
EN VOUT NC
SOT-23-5
Marking Information
For marking information, contact our sales representative directly or through a Richtek distributor located in your area.
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GND VOUT LX (TAB)
SOT-89
DS9261B-16 April 2011 |
www.richtek.com |
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RT9261B
Typical Application Circuit
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D1 |
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1N5819 |
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L1 |
RT9261B |
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LX |
VOUT |
VOUT |
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GND |
+ |
VIN |
COUT |
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22µF |
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D1 |
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1N5819 |
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L1 |
LX |
RT9261B |
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VOUT |
VOUT |
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+ |
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VIN |
EN |
GND |
COUT |
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22µF |
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* L1 ranges from 27μH to 120μH
Functional Pin Description
Pin No. |
Pin Name |
Pin Function |
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SOT-23-5 |
SOT-89 |
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1 |
-- |
EN |
Chip Enable (Active High). |
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2 |
2 |
VOUT |
Output Voltage. |
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3 |
-- |
NC |
No Internal Connection. |
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4 |
1 |
GND |
Ground. |
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5 |
3 |
LX |
Pin for Switching. |
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Function Block Diagram
LX |
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VLX Limiter |
VREF |
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LXSW |
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Buffer |
VOUT |
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GND |
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- |
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OSC 190kHz |
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+ |
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Error |
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Amplifier |
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Chip Enable |
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EN |
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www.richtek.com |
DS9261B-16 April 2011 |
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RT9261B |
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Absolute Maximum Ratings |
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z Output Voltage ------------------------------------------------------------------------------------------------------ |
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8V |
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z LX Pin Voltage ------------------------------------------------------------------------------------------------------- |
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8V |
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z EN Pin Voltage(1) ---------------------------------------------------------------------------------------------------- |
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−0.3 to VOUT +0.3V |
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z LX Pin Output Current --------------------------------------------------------------------------------------------- |
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400mA |
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z Power Dissipation, PD @ TA = 25°C |
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SOT-89 ---------------------------------------------------------------------------------------------------------------- |
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0.5W |
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SOT-23-5-------------------------------------------------------------------------------------------------------------- |
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0.25W |
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z Package Thermal Resistance |
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SOT-89, θJC ---------------------------------------------------------------------------------------------------------- |
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100°C/W |
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SOT-89, θJA ---------------------------------------------------------------------------------------------------------- |
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300°C/W |
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SOT-23-5, θJA -------------------------------------------------------------------------------------------------------- |
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250°C/W |
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z Operating Temperature Range ----------------------------------------------------------------------------------- |
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−20 to +85°C |
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z Storage Temperature Range -------------------------------------------------------------------------------------- |
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−65°C to 150°C |
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z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ |
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260°C |
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Notes: (1) Applicable to RT9261B-xxCB |
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Electrical Characteristics (Refer to Figure 1) |
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Parameter |
Symbol |
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Test Conditions |
Min |
Typ |
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Max |
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Unit |
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Output Voltage Accuracy |
VOUT |
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-2 |
-- |
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+2 |
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% |
Input Voltage |
VIN |
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-- |
-- |
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7 |
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V |
Start-up Voltage |
VST |
IOUT = 1mA, VIN: 0 → 2V |
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0.8 |
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1 |
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V |
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Hold-on Voltage |
VHO |
IOUT = 1mA, VIN: 2 → 0V |
0.7 |
-- |
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-- |
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V |
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Input Current 1 |
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VIN in continuous |
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VOUT ≤ 3.5V (1) |
-- |
24 |
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36 |
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μA |
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switching |
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3.5V < VOUT ≤ 5V (2) |
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36 |
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45 |
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Input Current 2 (1) (2) |
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VOUT in switch off condition |
-- |
6.5 |
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10 |
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μA |
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Input Current 3 (guaranteed by |
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V |
in no load |
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VOUT ≤ 3.5V (1) |
-- |
18 |
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36 |
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μA |
I1 and I2) |
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3.5V < VOUT ≤ 5V (2) |
-- |
20 |
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45 |
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IN |
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LX Switching Current |
ISWITCHING |
VLX = 0.4V |
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VOUT ≤ 3.5V (1) |
120 |
-- |
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-- |
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mA |
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3.5V < VOUT ≤ 5V (2) |
160 |
-- |
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-- |
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LX Leakage Current |
ILEAKAGE |
VLX = 6V |
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-- |
-- |
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0.5 |
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μA |
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Maximum Oscillator Frequency |
FMAX |
VOUT = 2.5V to 5V |
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140 |
190 |
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240 |
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kHz |
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VOUT = 1.5V to 2.4V |
140 |
190 |
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320 |
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kHz |
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Oscillator Duty Cycle |
DOSC |
On (VLX “L”) side |
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VOUT = 2.5V to 5V |
65 |
75 |
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85 |
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% |
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VOUT = 1.5V to 2.4V |
60 |
70 |
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80 |
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% |
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Efficiency |
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80 |
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-- |
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% |
VLX Voltage Limit |
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LX switch on |
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0.65 |
0.8 |
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1.0 |
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V |
Notes:
(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= 25°C, and External Circuit of Typical Application
DS9261B-16 April 2011 |
www.richtek.com |
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