Richtek RT8068AZQW, RT8068AZSP Schematic [ru]

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®
3A, 1MHz, Synchronous Step-Down Converter
RT8068A
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 V
while delivering up to 3A of output current.
IN
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 require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
RT8068AZQW
13 : Product Code
13 YM
DNN
YMDNN : Date Code
Features

High Efficiency : Up to 95%


Low R

Internal Switches : 69m
DS(ON)
ΩΩ
Ω/49m
ΩΩ
= 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
Notebook Computers
Distrib uted Power Systems
IP Phones
Digital Cameras
Pin Configurations
(TOP VIEW)
GND
GND
11
9
10
PVIN
9
PVIN
8
SVIN
7
NC
6
FB
8
PVIN
7
PVIN
6
SVIN
5
FB
1
LX
2
LX
3
LX
EN
4
5
PGOOD
WDFN-10L 3x3
LX
2
LX
PGOOD
EN
3
4
SOP-8 (Exposed Pad)
ΩΩ
Ω at V
ΩΩ
IN
RT8068AZSP
RT8068AZSP : Product Code
RT8068A
YMDNN : Date Code
ZSPYMDNN
Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
DS8068A-05 June 2015 www.richtek.com
©
1
RT8068A
Typical Application Circuit
PGOOD
V
IN
Chip Enable
R1 100k
C
10µF
RT8068A
PGOOD
PVIN
IN
C1
1µF
SVIN
EN
LX
FB
GND
L
C
OUT
C
R
FB1
R
FB2
FF
Table 1. Recommended Component Selection
V
(V) R
OUT
(k) R
FB1
(k) C
FB2
(pF) L (H) C
FF
3.3 229.5 51 22 2 22 x 2
2.5 161.5 51 22 2 22 x 2
1.8 102 51 22 1.5 22 x 2
1.5 76.5 51 22 1.5 22 x 2
1.2 51 51 22 1.5 22 x 2
1.0 34 51 22 1.5 22 x 2
OUT
V
OUT
(F)
Functional Pin Description
Pin No.
WDFN-10L
SOP-8
(Exposed Pad)
1, 2, 3 1, 2 LX Switch Node. Connect this pin to the induc tor.
4 3 PGOOD
5 4 EN Enable Contro l. P ull high to turn on. Do not fl oat.
6 5 FB
7 -- NC No Internal Connection.
8 6 SVIN
9,10 7,8 PVI N
11
(Exposed Pad)
(Exposed Pad)
9
Pin
Name
GND
Pin Function
Power Good Indicator. This pin is an open drain logic output that is pulled to ground when the output voltage is less than 90 % of the target output voltage. Hysteresis = 5%.
Feedback Pin. Th is pin receives the feedback voltage from a resistive voltage divider connected ac ross the output.
Signal Input Pin. Decouple th is pin to GND wit h a t least 1F ceramic cap. Power Input Pin. Decouple this pin to GND with at least 4.7F ceramic cap. Ground. The exposed pa d must be soldered t o a large PCB and connected to GND for maximum power dissipation.
Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
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DS8068A-05 June 2015www.richtek.com
Function Block Diagram
RT8068A
EN
PGOOD
FB
PGOOD
V
REF
0.6V
EA
POR
SVIN
Int-SS
EN
Output Clamp
0.72V
0.54V
0.4V
OSC
OV
PGOOD
UV
Slope
Com
Control
Logic
OTP
ISEN
OC
Limit
PVIN
Driver
LX
NISEN
Zero Current
100
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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RT8068A
Absolute Maximum Ratings (Note 1)
Supply Input Voltage, PVIN, SVIN ------------------------------------------------------------------------------------- 0.3V to 6.5V
LX Pin
DC----------------------------------------------------------------------------------------------------------------------------- 0.3V to 6.8V
< 20ns ----------------------------------------------------------------------------------------------------------------------- 2.5V to 9V
Other I/O Pin Voltage ----------------------------------------------------------------------------------------------------- 0.3V to 6.5V
Power Dissipation, P
WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------------- 1.429W
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------------- 1.333W
Package Thermal Resistance (Note 2)
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)
HBM (Human Body Model)---------------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ----------------------------------------------------------------------------------------------------- 200V
@ TA = 25°C
D
Recommended Operating Conditions
Supply Input Voltage, PVIN, SVIN ------------------------------------------------------------------------------------- 2.7V to 5.5V
Junction Temperature Range -------------------------------------------------------------------------------------------- 40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- 40°C to 85°C
(Note 4)
Electrical Characteristics
(VIN = 3.3V, T
Feedback Reference Voltage V
Feedback Leakage Current IFB -- 0.1 0.4 A
DC Bias Current
Output Voltage Line Regulation
Output Voltage Load Regulation I Switch Leakage Current -- -- 1 A
Switching Frequency 0.8 1 1.2 MHz
Switch On Resistance, High R
Switch On Resistance, Low R
P-MOSFET Current Limit I
Copyright 2015 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
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= 25°C, unless otherwise specified)
A
Parameter Symbol Test Conditions Min Typ Max Unit
0.594 0.6 0.606 V
REF
Active , V Switching
= 0.7V, Not
FB
-- 110 140
A
Shutdown -- -- 1
= 2.7V to 5.5V
V
IN
I
= 0A
OUT
= 0A to 3A 1 -- 1 %
OUT
DS(ON)_P
DS(ON)_N
LIM
VIN = 5V -- 69 -- m
VIN = 5V -- 49 -- m
4 -- -- A
-- 0.3 -- %/V
DS8068A-05 June 2015www.richtek.com
Parameter Symbol Test Conditions Min Typ Max Unit
Under Voltage Lockout
Threshold
V
UVLO
RT8068A
Rising 2.2 2.4 2.6
V
IN
VIN Falling 2 2.2 2.4
V
EN Input
Threshold Voltage
Logic-High V
Logic-Low VIL -- -- 0.4
1.6 -- --
IH
V
EN Pull Low Resistance -- 500 -- k
Over Temperature Protection TSD -- 150 -- C
Over Temperature Protection
Hysteresis
-- 20 -- C
Soft-Start Time tSS 500 -- -- s
V
Discharge Resistance -- 100 --
OUT
V
Over Voltage Protection
OUT
(Latch-Off, Delay Time = 10s)
V
Under Voltage Lock Out
OUT
(Latch-Off)
Power Good
115 120 130 %
57 66 75 %
Measured FB, With Respect to
V
REF
85 90 -- %
Power Good Hysteresis -- 5 -- %
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. θ
Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions.
is measured at T
JA
measured at the exposed pad of the package.
= 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
A
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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