Richtek RT8068AZQW, RT8068AZSP Schematic [ru]
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®
RT8068A
3A, 1MHz, Synchronous Step-Down Converter
General Description
The RT8068A is a high efficiency synchronous, step-down DC/DC converter. It's input voltage range from 2.7V to 5.5V that provides an adjustable regulated output voltage from 0.6V to VIN while delivering up to 3A of output current. The internal synchronous low on resistance power switches increase efficiency and eliminate the need for an external Schottky diode. The switching frequency is fixed internally at 1MHz. The 100% duty cycle provides low dropout operation, hence extending battery life in portable systems. Current mode operation with internal compensation allows the transient response to be optimized over a wide range of loads and output capacitors. The RT8068A is available in WDFN-10L 3x3 and SOP-8 (Exposed Pad) packages.
Ordering Information
RT8068A
Package Type
QW : WDFN-10L 3x3 (W-Type) SP : SOP-8 (Exposed Pad-Option 2)
Lead Plating System
Z : ECO (Ecological Element with Halogen Free and Pb free)
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.
Marking Information
RT8068AZQW
13 : Product Code
13 YM YMDNN : Date Code
DNN
RT8068AZSP
RT8068AZSP : Product Code
RT8068A YMDNN : Date Code
ZSPYMDNN
Features
High Efficiency : Up to 95%
Low RDS(ON) Internal Switches : 69mΩ/49mΩ at VIN = 5V
Fixed Frequency : 1MHz
No Schottky Diode Required
Internal Compensation
0.6V Reference Allows Low Output Voltage
Low Dropout Operation : 100% Duty Cycle
OCP, UVP, OVP, OTP
RoHS Compliant and Halogen Free
Applications
Portable Instruments
Battery Powered Equipment
Notebook Computers
Distrib uted Power Systems
IP Phones
Digital Cameras
Pin Configurations
(TOP VIEW)
LX |
1 |
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10 |
PVIN |
LX |
2 |
GND |
9 |
PVIN |
LX |
3 |
8 |
SVIN |
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PGOOD 4 |
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7 |
NC |
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EN 5 |
11 |
6 |
FB |
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WDFN-10L 3x3 |
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LX |
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8 |
PVIN |
LX |
2 |
GND |
7 |
PVIN |
PGOOD |
3 |
9 |
6 |
SVIN |
EN |
4 |
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5 |
FB |
SOP-8 (Exposed Pad)
Copyright ©2015 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
DS8068A-05 June 2015 |
www.richtek.com |
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1 |
RT8068A
Typical Application Circuit
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RT8068A |
L |
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PGOOD |
R1 |
PGOOD |
LX |
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VOUT |
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COUT |
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100k |
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CFF |
V |
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PVIN |
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RFB1 |
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IN |
CIN |
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SVIN |
FB |
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10µF |
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C1 |
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RFB2 |
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1µF |
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Chip Enable |
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EN |
GND |
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Table 1. Recommended Component Selection
VOUT (V) |
RFB1 (k ) |
RFB2 (k ) |
CFF (pF) |
L ( H) |
COUT ( F) |
3.3 |
229.5 |
51 |
22 |
2 |
22 x 2 |
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2.5 |
161.5 |
51 |
22 |
2 |
22 x 2 |
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1.8 |
102 |
51 |
22 |
1.5 |
22 x 2 |
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1.5 |
76.5 |
51 |
22 |
1.5 |
22 x 2 |
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1.2 |
51 |
51 |
22 |
1.5 |
22 x 2 |
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1.0 |
34 |
51 |
22 |
1.5 |
22 x 2 |
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Functional Pin Description
Pin No. |
Pin |
Pin Function |
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SOP-8 |
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WDFN-10L |
Name |
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(Exposed Pad) |
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1, 2, 3 |
1, 2 |
LX |
Switch Node. Connect this pin to the inductor. |
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Power Good Indicator. This pin is an open drain logic output that is |
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4 |
3 |
PGOOD |
pulled to ground when the output voltage is less than 90% of the |
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target output voltage. Hysteresis = 5%. |
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5 |
4 |
EN |
Enable Control. Pull high to turn on. Do not float. |
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6 |
5 |
FB |
Feedback Pin. This pin receives the feedback |
voltage from a |
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resistive voltage divider connected across the output. |
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7 |
-- |
NC |
No Internal Connection. |
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8 |
6 |
SVIN |
Signal Input Pin. Decouple this pin to GND with at least 1 F ceramic |
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cap. |
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9,10 |
7,8 |
PVIN |
Power Input Pin. Decouple this pin to GND with |
at least 4.7 F |
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ceramic cap. |
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11 |
9 |
GND |
Ground. The exposed pad must be soldered to a large PCB and |
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(Exposed Pad) |
(Exposed Pad) |
connected to GND for maximum power dissipation. |
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Copyright ©2015 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
www.richtek.com |
DS8068A-05 June 2015 |
2 |
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RT8068A
Function Block Diagram
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EN |
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EN |
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ISEN |
PVIN |
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PGOOD |
PGOOD |
OSC |
Slope |
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Com |
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VREF |
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0.6V |
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EA |
Output |
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OC |
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FB |
Clamp |
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Limit |
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Int-SS |
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Driver |
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0.72V |
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Control |
LX |
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OV |
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Logic |
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0.54V |
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PGOOD |
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NISEN |
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Zero Current |
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0.4V |
UV |
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POR |
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OTP |
100 |
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SVIN |
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Copyright ©2015 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
DS8068A-05 June 2015 |
www.richtek.com |
|
3 |
RT8068A
Absolute Maximum Ratings (Note 1)
Supply Input Voltage, PVIN, SVIN------------------------------------------------------------------------------------- |
−0.3V to 6.5V |
LX Pin |
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DC ----------------------------------------------------------------------------------------------------------------------------- |
−0.3V to 6.8V |
< 20ns ----------------------------------------------------------------------------------------------------------------------- |
−2.5V to 9V |
Other I/O Pin Voltage ----------------------------------------------------------------------------------------------------- |
−0.3V to 6.5V |
Power Dissipation, PD @ TA = 25°C |
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WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------------- |
1.429W |
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------------- |
1.333W |
Package Thermal Resistance (Note 2) |
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WDFN-10L 3x3, θJA ------------------------------------------------------------------------------------------------------- |
70°C/W |
WDFN-10L 3x3, θJC ------------------------------------------------------------------------------------------------------- |
8.2°C/W |
SOP-8 (Exposed Pad), θJA ---------------------------------------------------------------------------------------------- |
75°C/W |
SOP-8 (Exposed Pad), θJC --------------------------------------------------------------------------------------------- |
15°C/W |
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- |
260°C |
Junction Temperature ----------------------------------------------------------------------------------------------------- |
150°C |
Storage Temperature Range -------------------------------------------------------------------------------------------- |
−65°C to 150°C |
ESD Susceptibility (Note 3) |
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HBM (Human Body Model) ---------------------------------------------------------------------------------------------- |
2kV |
MM (Machine Model) ----------------------------------------------------------------------------------------------------- |
200V |
Recommended Operating Conditions |
(Note 4) |
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Supply Input Voltage, PVIN, SVIN |
------------------------------------------------------------------------------------- |
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2.7V to 5.5V |
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Junction Temperature Range -------------------------------------------------------------------------------------------- |
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−40°C to 125°C |
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Ambient Temperature Range -------------------------------------------------------------------------------------------- |
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−40°C to 85°C |
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Electrical Characteristics |
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(VIN = 3.3V, TA = 25°C, unless otherwise specified) |
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Parameter |
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Symbol |
Test Conditions |
Min |
Typ |
Max |
Unit |
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Feedback Reference Voltage |
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VREF |
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0.594 |
0.6 |
0.606 |
V |
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Feedback Leakage Current |
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IFB |
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-- |
0.1 |
0.4 |
A |
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Active , VFB = 0.7V, Not |
-- |
110 |
140 |
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DC Bias Current |
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Switching |
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A |
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Shutdown |
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-- |
-- |
1 |
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Output Voltage Line Regulation |
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VIN = 2.7V to 5.5V |
-- |
0.3 |
-- |
%/V |
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IOUT = 0A |
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Output Voltage Load Regulation |
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IOUT = 0A to 3A |
1 |
-- |
1 |
% |
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Switch Leakage Current |
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-- |
-- |
1 |
A |
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Switching Frequency |
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0.8 |
1 |
1.2 |
MHz |
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Switch On Resistance, High |
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RDS(ON)_P |
VIN = 5V |
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-- |
69 |
-- |
m |
Switch On Resistance, Low |
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RDS(ON)_N |
VIN = 5V |
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-- |
49 |
-- |
m |
P-MOSFET Current Limit |
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ILIM |
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4 |
-- |
-- |
A |
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Copyright ©2015 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
|||||||
www.richtek.com |
DS8068A-05 June 2015 |
4 |
|
RT8068A
Parameter |
Symbol |
Test Conditions |
Min |
Typ |
Max |
Unit |
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Under Voltage Lockout |
VUVLO |
VIN Rising |
2.2 |
2.4 |
2.6 |
V |
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Threshold |
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VIN Falling |
2 |
2.2 |
2.4 |
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EN Input |
Logic-High |
VIH |
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1.6 |
-- |
-- |
V |
Threshold Voltage |
Logic-Low |
VIL |
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-- |
-- |
0.4 |
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EN Pull Low Resistance |
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-- |
500 |
-- |
k |
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Over Temperature Protection |
TSD |
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-- |
150 |
-- |
C |
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Over Temperature Protection |
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-- |
20 |
-- |
C |
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Hysteresis |
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Soft-Start Time |
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tSS |
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500 |
-- |
-- |
s |
VOUT Discharge Resistance |
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-- |
100 |
-- |
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VOUT Over Voltage Protection |
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115 |
120 |
130 |
% |
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(Latch-Off, Delay Time = 10 s) |
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VOUT Under Voltage Lock Out |
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57 |
66 |
75 |
% |
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(Latch-Off) |
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Power Good |
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Measured FB, With Respect to |
85 |
90 |
-- |
% |
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VREF |
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Power Good Hysteresis |
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-- |
5 |
-- |
% |
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Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and 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 may affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright ©2015 Richtek Technology Corporation. All rights reserved. |
is a registered trademark of Richtek Technology Corporation. |
DS8068A-05 June 2015 |
www.richtek.com |
|
5 |