RT8008
1.5MHz, 600mA, High Efficiency PWM Step-Down DC/DC Converter
General Description
The RT8008 is a high-efficiency pulse-width-modulated (PWM) step-down DC/DC converter. Capable of delivering 600mA output current over a wide input voltage range from 2.5V to 5.5V, the RT8008 is ideally suited for portable electronic devices that are powered from 1-cell Li-ion battery or from other power sources within the range such as cellular phones, PDAs and handy-terminals.
Internal synchronous rectifier with low RDS(ON) dramatically reduces conduction loss at PWM mode. No external Schottky diode is required in practical application. The RT8008 automatically turns off the synchronous rectifier while the inductor current is low and enters discontinuous PWM mode. This can increase efficiency at light load condition.
The RT8008 enters Low-Dropout mode when normal PWM cannot provide regulated output voltage by continuously turning on the upper P-MOSFET. RT8008 enter shutdown mode and consumes less than 0.1μAwhen ENpin is pulled low.
The switching ripple is easily smoothed-out by small package filtering elements due to a fixed operation frequency of 1.5MHz. This along with small SOT-23-5 and TSOT-23-5 package provides small PCB area application. Other features include soft start, lower internal reference voltage with 2% accuracy, over temperature protection, and over current protection.
Pin Configurations
(TOP VIEW)
FB/VOUT VIN
5 4
2 3
EN GND LX
SOT-23-5/TSOT-23-5
Marking Information
For marking information, contact our sales representative directly or through a Richtek distributor located in your area.
Features
z2.5V to 5.5V Input Range
zAdjustable Output From 0.6V to VIN
z1.0V, 1.2V, 1.5V, 1.8V, 2.5V and 3.3V Fixed/ Adjustable Output Voltage
z600mA Output Current, 1A Peak Current
z95% Efficiency
zNo Schottky Diode Required
z1.5MHz Fixed Frequency PWM Operation
zSmall SOT-23-5 and TSOT-23-5 Package
zRoHS Compliant and 100% Lead (Pb)-Free
Applications
zCellular Telephones
zPersonal Information Appliances
zWireless and DSL Modems
zMP3 Players
zPortable Instruments
Ordering Information
RT8008(-)
Package Type
B : SOT-23-5
J5 : TSOT-23-5
Lead Plating System P : Pb Free
G : Green (Halogen Free and Pb Free)
Output Voltage Default : Adjustable 10 : 1.0V
12 : 1.2V
15 : 1.5V
18 : 1.8V
25 : 2.5V
33 : 3.3V
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.
DS8008-07 March 2011 |
www.richtek.com |
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RT8008
Typical Application Circuit
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L |
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VIN |
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4 |
VIN |
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LX |
3 |
2.2µH |
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VOUT |
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2.2V to 5.5V |
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CIN |
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RT8008 |
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4.7µF |
1 |
5 |
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COUT |
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EN |
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VOUT |
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10µF |
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GND |
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Figure 1. Fixed Voltage Regulator
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L |
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VIN |
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4 VIN |
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LX |
32.2µH |
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VOUT |
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2.2V to 5.5V |
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CIN |
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C1 |
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4.7µF |
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RT8008 |
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1 |
5 |
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R1 |
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COUT |
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EN |
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FB |
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10µF |
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R1 |
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GND |
IR2 |
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R2 |
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2 |
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VOUT = VREF x 1 |
+ |
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R2 |
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with R2 = 300kΩ to 60kΩ so the IR2 = 2μA to 10μA,
and (R1 x C1) should be in the range between 3x10-6 and 6x10-6 for component selection.
Figure 2. Adjustable Voltage Regulator
Layout Guide
VIN |
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GND |
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VOUT |
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VIN |
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GND |
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VOUT |
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C |
IN |
C |
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C |
IN |
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C |
OUT |
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OUT |
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L |
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L |
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VIN |
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4 |
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3 |
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LX |
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VIN |
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4 |
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3 |
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LX |
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2 |
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GND |
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2 |
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GND |
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C1 |
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VOUT |
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5 |
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1 |
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EN |
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FB |
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5 |
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1 |
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EN |
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R1 |
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R2 |
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VOUT |
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GND |
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GND |
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Figure 3
Layout note:
1.The distance that CIN connects to VIN is as close as possible (Under 2mm).
2.COUT should be placed near RT8008.
www.richtek.com |
DS8008-07 March 2011 |
2 |
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RT8008 |
Functional Pin Description |
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Pin Number |
Pin Name |
Pin Function |
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1 |
EN |
Chip Enable (Active High, do not leave EN pin floating, and VEN < VIN + 0.6V). |
2 |
GND |
Ground. |
3 |
LX |
Pin for Switching. |
4 |
VIN |
Power Input. |
5 |
FB/VOUT |
Feedback Input Pin. |
Function Block Diagram
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EN |
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VIN |
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OSC & |
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RS1 |
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Current |
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Shutdown |
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Limit |
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Control |
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Slope |
Detector |
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Compensation |
Current |
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Sense |
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Control |
Driver |
LX |
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PWM |
Logic |
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FB/VOUT |
Error |
Comparator |
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Amplifier |
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RC |
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UVLO & |
Zero |
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RS2 |
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COMP |
Detector |
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Power Good |
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Detector |
VREF |
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GND |
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DS8008-07 March 2011 |
www.richtek.com |
3
RT8008
Absolute Maximum Ratings (Note 1)
Supply Input Voltage ------------------------------------------------------------------------------------------------------ |
6.5V |
Enable, FB Voltage ------------------------------------------------------------------------------------------------------- |
VIN + 0.6V |
Power Dissipation, PD @ TA = 25°C |
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SOT-23-5, TSOT-23-5 ----------------------------------------------------------------------------------------------------- |
0.4W |
Package Thermal Resistance (Note 2) |
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SOT-23-5, TSOT-23-5, θJA ----------------------------------------------------------------------------------------------- |
250°C/W |
SOT-23-5, TSOT-23-5, θJC ----------------------------------------------------------------------------------------------- |
130°C/W |
Junction Temperature Range -------------------------------------------------------------------------------------------- |
150°C |
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- |
260°C |
Storage Temperature Range -------------------------------------------------------------------------------------------- |
−65°C to 150°C |
ESD Susceptibility (Note 3) |
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HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- |
2kV |
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ |
200V |
Recommended Operating Conditions |
(Note 4) |
Supply Input Voltage ------------------------------------------------------------------------------------------------------ |
2.5V to 5.5V |
Junction Temperature Range -------------------------------------------------------------------------------------------- |
−40°C to 125°C |
Ambient Temperature Range -------------------------------------------------------------------------------------------- |
−40°C to 85°C |
Electrical Characteristics
(VIN = 3.6V, VOUT = 2.5V, VREF = 0.6V, L = 2.2μH, CIN = 4.7μF, COUT = 10μF, TA = 25°C, IMAX = 600mA unless otherwise specified)
Parameter |
Symbol |
Test Conditions |
Min |
Typ |
Max |
Unit |
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Input Voltage Range |
VIN |
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2.5 |
-- |
5.5 |
V |
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Quiescent Current |
IQ |
IOUT = 0mA, VFB = VREF + 5% |
-- |
50 |
100 |
μA |
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Shutdown Current |
ISHDN |
EN = GND |
-- |
0.1 |
1 |
μ |
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A |
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Reference Voltage |
VREF |
For adjustable output voltage |
0.588 |
0.6 |
0.612 |
V |
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Adjustable Output Range |
VOUT |
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VREF |
-- |
VIN − 0.2 |
V |
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VOUT |
VIN = 2.2 to 5.5V, VOUT = 1.0V |
−3 |
-- |
3 |
% |
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0A < IOUT < 600mA |
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VOUT |
VIN = 2.2 to 5.5V, VOUT = 1.2V |
−3 |
-- |
3 |
% |
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0A < IOUT < 600mA |
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VOUT |
VIN = 2.2 to 5.5V, VOUT = 1.5V |
−3 |
-- |
3 |
% |
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0A < IOUT < 600mA |
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Fix |
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VOUT |
VIN = 2.2 to 5.5V, VOUT = 1.8V |
−3 |
-- |
3 |
% |
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Output Voltage |
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0A < IOUT < 600mA |
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VIN = 2.8 to 5.5V, VOUT = 2.5V |
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Accuracy |
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VOUT |
−3 |
-- |
3 |
% |
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0A < IOUT < 600mA |
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VOUT |
VIN = 3.5 to 5.5V, VOUT = 3.3V |
−3 |
-- |
3 |
% |
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0A < IOUT < 600mA |
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VIN = VOUT + 0.2V to 5.5V, VIN 3.5V |
−3 |
-- |
3 |
% |
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Adjustable |
VOUT |
0A < IOUT < 600mA |
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VIN = VOUT + 0.4V to 5.5V, VIN 2.2V |
−3 |
-- |
3 |
% |
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0A < IOUT < 600mA |
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To be continued |
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www.richtek.com |
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DS8008-07 March 2011 |
||||
4 |
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RT8008
Parameter |
Symbol |
Test Conditions |
Min |
Typ |
Max |
Unit |
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FB Input Current |
IFB |
VFB = VIN |
−50 |
-- |
50 |
nA |
||
PMOSFET RON |
PRDS(ON) |
IOUT = 200mA |
VIN = 3.6V |
-- |
0.3 |
-- |
Ω |
|
VIN = 2.5V |
-- |
0.4 |
-- |
|||||
|
|
|
|
|||||
NMOSFET RON |
NRDS(ON) |
IOUT = 200mA |
VIN = 3.6V |
-- |
0.25 |
-- |
Ω |
|
VIN = 2.5V |
-- |
0.35 |
-- |
|||||
|
|
|
|
|||||
P-Channel Current Limit |
IP(LM) |
VIN = 2.5V to 5.5 V |
1 |
-- |
1.8 |
A |
||
EN High-Level Input Voltage |
VENH |
VIN = 2.5V to 5.5V |
1.5 |
-- |
-- |
V |
||
|
|
|
|
|
|
|
||
EN Low-Level Input Voltage |
VENL |
VIN = 2.5V to 5.5V |
-- |
-- |
0.4 |
V |
||
Under Voltage Lockout Threshold |
|
|
|
-- |
1.8 |
-- |
V |
|
|
|
|
|
|
|
|
|
|
Hysteresis |
|
|
|
-- |
0.1 |
-- |
V |
|
|
|
|
|
|
|
|
||
Oscillator Frequency |
fOSC |
VIN = 3.6V, IOUT = 100mA |
1.2 |
1.5 |
1.8 |
MHz |
||
Thermal Shutdown Temperature |
TSD |
|
|
-- |
160 |
-- |
°C |
|
Min. On Time |
|
|
|
-- |
50 |
-- |
ns |
|
|
|
|
|
|
|
|
|
|
Max. Duty Cycle |
|
|
|
100 |
-- |
-- |
% |
|
|
|
|
|
|
|
|
||
LX Leakage Current |
|
VIN = 3.6V, VLX = 0V or VLX = 3.6V |
−1 |
-- |
1 |
μA |
Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability.
Note 2. θJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Pin 2 of SOT-23-5/TSOT-23-5 packages is the case position for θJC measurement.
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
DS8008-07 March 2011 |
www.richtek.com |
|
5 |