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RT9261/A |
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VFM Step-Up DC/DC Converter |
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General Description |
Features |
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The RT9261 Series are VFM Step-upDC/DC ICs with ultra |
z Minimal Number of External Components ( Only |
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low supply current by CMOS process and suitable for |
an Inductor, a Diode, and a Capacitor) |
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use with battery-powered instruments. |
z Ultra Low Input Current ( 5μA at Switch Off) |
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The RT9261 IC consists of an oscillator, a VFM control |
z ±2% High Output Voltage Accuracy |
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z Low Ripple and Low Noise |
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circuit, a driver transistor (LX switch), a reference voltage |
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z Low Start-up Voltage, 0.85V at 1mA |
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unit, an error amplifier, resistors for voltage detection, and |
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z 75% Efficiency with Low Cost Inductor |
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a LX switch protection circuit. A low ripple and high |
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z +50 ppm/ °C Low Temperature-Drift |
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efficiency step-up DC/DC converter can be constructed of |
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z SOT-89 and SOT-23-5 Small Packages |
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this RT9261 IC with only three external components. |
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z RoHS Compliant and 100% Lead (Pb)-Free |
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The RT9261A IC provides with a drive pin (EXT) for an |
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Applications |
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external transistor, so that a power transistor can be |
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externally applied. Therefore, the RT9261A IC is |
z Power source for battery-powered equipment |
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recommended for applications where large currents are |
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z Power source for cameras, camcorders, VCRs, PDAs, |
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required. EN pin enables circuit to set the standby supply |
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pagers, electronic data banks, and hand-held |
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current at a maximum of 0.5μA. |
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communication equipment |
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Ordering Information |
z Power source for applications, which require higher |
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voltage than that of batteries used in the appliances |
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RT9261/A- |
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Package Type |
Pin Configurations |
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B : SOT-23-5 |
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X : SOT-89 |
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(TOP VIEW) |
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Lead Plating System |
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P : Pb Free |
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G : Green (Halogen Free and Pb Free) |
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Output Voltage |
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15 |
: 1.5V |
1 |
2 |
3 |
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2 |
3 |
16 |
: 1.6V |
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GND VOUT |
LX |
GND VOUT EXT |
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49 |
: 4.9V |
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50 |
: 5.0V |
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(TAB) |
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(TAB) |
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RT9261 |
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RT9261A |
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Use external switch |
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SOT-89 |
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Use internal switch |
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Note : |
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Richtek products are : |
LX |
GND |
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EXT |
GND |
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` RoHS compliant and compatible with the current require- |
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ments of IPC/JEDEC J-STD-020. |
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` Suitable for use in SnPb or Pb-free soldering processes. |
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Marking Information |
EN VOUT NC |
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EN VOUT NC |
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RT9261 |
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RT9261A |
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For marking information, contact our sales representative |
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SOT-23-5 |
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directly or through a Richtek distributor located in your |
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area. |
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DS9261/A-16 April 2011 |
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www.richtek.com |
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1 |
RT9261/A
Typical Application Circuit
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D1 |
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1N5819 |
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L1 |
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RT9261xX |
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100µH |
LX |
VOUT |
VOUT |
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GND |
+ |
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VIN |
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COUT |
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22µF |
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Figure 1
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D1 |
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1N5819 |
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L1 |
RT9261xB |
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100µH |
LX |
VOUT |
VOUT |
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+ |
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VIN |
NC |
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COUT |
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22µF |
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EN |
GND |
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L1 |
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D1 |
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27µH |
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1N5819 |
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Cb |
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RT9261AxX |
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0.01µF |
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VIN |
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EXT |
VOUT |
VOUT |
ZTX |
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GND |
+ |
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COUT |
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650 Tr |
Rb |
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22µF |
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300 |
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Figure 2
L1 |
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D1 |
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27µH |
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1N5819 |
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VIN |
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NC |
RT9261AxB |
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Cb |
VOUT |
+ |
VOUT |
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0.01µF |
EXT |
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COUT |
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ZTX |
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22µF |
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EN GND |
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650 |
Tr |
Rb |
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300 |
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Figure 3 |
Figure 4 |
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D1 |
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1N5819 |
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L1 |
RT9261xB |
VOUT |
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27µH |
LX |
VOUT |
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+ |
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VIN |
NC |
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COUT |
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22µF |
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Chip |
EN |
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GND |
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Enable |
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Figure 5
www.richtek.com |
DS9261/A-16 April 2011 |
2 |
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RT9261/A |
Functional Pin Description |
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Pin No. |
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Pin Name |
Pin Function |
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RT9261-□□□X |
RT9261A-□□□X |
RT9261-□□□B |
RT9261A-□□□B |
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1 |
1 |
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4 |
4 |
GND |
Ground. |
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2 |
2 |
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2 |
2 |
VOUT |
Output Voltage. |
3 |
-- |
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5 |
-- |
LX |
Pin for Switching. |
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-- |
3 |
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-- |
5 |
EXT |
Drive External Device. |
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-- |
-- |
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1 |
1 |
EN |
Chip Enable (Active High). |
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-- |
-- |
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3 |
3 |
NC |
No Internal Connected. |
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Function Block Diagram
LX |
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VLX Limiter |
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VREF |
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LXSW |
Buffer |
VOUT |
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GND |
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VFM Control |
- |
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+ |
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EXT |
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Error |
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OSC 100kHz |
Amplifier |
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Chip Enable |
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EN |
Notes:
(1)LX Pin...... only for 9261- xX and 9261- xB
(2)EXT Pin.... only for 9261A- xX and 9261A-xB
(3)EN Pin...... only for 9261- xB and 9261A- xB
DS9261/A-16 April 2011 |
www.richtek.com |
3
RT9261/A
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 EN 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 |
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SOT-89 ---------------------------------------------------------------------------------------------------------------- |
0.5W |
SOT-23-5-------------------------------------------------------------------------------------------------------------- |
0.25W |
z Package Thermal Resistance |
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SOT-89, θJC ---------------------------------------------------------------------------------------------------------- |
100°C/W |
SOT-89, θJA ---------------------------------------------------------------------------------------------------------- |
300°C/W |
SOT-23-5, 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: |
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(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 |
Symbol |
Test Conditions |
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Min |
Typ |
Max |
Unit |
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Output Voltage Accuracy |
VOUT |
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−2 |
-- |
2 |
% |
Input Voltage |
VIN |
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-- |
-- |
7 |
V |
Start-up Voltage |
VST |
IOUT = 1mA, VIN: 0 → 2V |
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-- |
0.85 |
1 |
V |
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Hold-on Voltage |
VHO |
IOUT = 1mA, VIN: 2 → 0V |
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0.7 |
-- |
-- |
V |
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V |
≤ 3.5V (1) |
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-- |
15 |
18 |
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Input Current 1 |
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VIN at no load |
OUT |
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μA |
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3.5V < VOUT ≤ |
5V |
(2) |
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18 |
24 |
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Input Current 2 |
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VOUT in switch off condition |
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5 |
8 |
μA |
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LX Switching Current |
ISWITCHING |
VLX = 0.4V |
VOUT ≤ 3.5V (1) |
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60 |
-- |
-- |
mA |
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3.5V < VOUT ≤ 5V (2) |
80 |
-- |
-- |
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LX Leakage Current |
ILEAKAGE |
VLX = 6V |
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0.5 |
μA |
Maximum Oscillator |
FMAX |
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80 |
120 |
160 |
kHz |
Oscillator Duty Cycle |
D |
On ( V ” L ” ) side |
VOUT = 2.5V to 5V |
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75 |
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% |
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OSC |
LX |
VOUT = 1.5V to 2.4V |
60 |
70 |
80 |
% |
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Efficiency |
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75 |
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VLX Voltage Limit |
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LX switch on |
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0.65 |
0.8 |
1 |
V |
Notes:
(1)Unless otherwise provided, VIN = 1.8V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and External Circuit of Typical Application (2)Unless otherwise provided, VIN = 3V, VSS = 0V, IOUT = 10mA, TOPT = 25°C, and External Circuit of Typical Application
www.richtek.com |
DS9261/A-16 April 2011 |
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