RT5771B [RICHTEK]
暂无描述;
| 型号： | RT5771B |
| 厂家： | 
RICHTEK TECHNOLOGY CORPORATION |
| 描述： | 暂无描述 |
| 文件： | 总13页 (文件大小：169K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
®
RT5771B
3A, 1MHz, Synchronous Step-Down Converter
General Description
Features
High Efficiency : Up to 95%
The RT5771B is a high efficiency synchronous, step-down
DC-DC converter. Its input voltage ranges 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 RT5771B is available in a WDFN-10L 3x3 package.
High Efficiency at Light Load
Low RDS(ON) Power Switches : 69mΩ/49mΩ
Fixed Frequency : 1MHz
No Schottky Diode Required
Internal Compensation
0.6V Reference Allows Low Output Voltage
Low Dropout Operation : 100% Duty Cycle
OCP, UVP, OTP
Applications
Portable Instruments
Battery Powered Equipment
Notebook Computers
Distributed Power Systems
IP Phones
Ordering Information
RT5771B
Package Type
QW : WDFN-10L 3x3 (W-Type)
Digital Cameras
Lead Plating System
G : Green (Halogen Free and Pb Free)
Pin Configuration
(TOP VIEW)
Note :
1
2
3
4
5
10
9
EN
PGOOD
NC
SW
FB
VCC
VIN
GND
GND
Richtek products are :
8
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.
7
11
6
SW
WDFN-10L 3x3
Marking Information
M3= : Product Code
YMDNN : Date Code
M3=YM
DNN
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS5771B-01 June 2019
www.richtek.com
1
RT5771B
Typical Application Circuit
L
RT5771B
1.5µH
6, 7
3
2
V
V
OUT
1.05V
VIN
IN
SW
C
C
10µF
OUT
IN
VCC
22µF x 2
C
FF
560pF
R1
6.2k
C1
1µF
R3
100k
1
FB
9
R2
8.2k
PGOOD
EN
PGOOD
Chip Enable
4, 5,
10
GND
11 (Exposed Pad)
Table 1. Recommended Component Selection
R1 (k)
37
R2 (k)
8.2
L (H)
2
VOUT (V)
3.3
CFF (pF)
430
COUT (F)
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
2.5
26
8.2
430
2
1.8
16.5
12.3
8.2
8.2
510
1.5
1.5
1.5
1.5
1.5
8.2
560
1.2
8.2
620
1
5.6
8.2
680
Functional Pin Description
Pin No.
Pin Name
Pin Function
Feedback input. This pin receives the feedback voltage from a resistive
voltage divider connected across the output.
1
FB
2
3
VCC
VIN
Supply voltage input. Decouple this pin to GND with at least 1F ceramic cap.
Power input. Decouple this pin to GND with at least 10F ceramic cap.
4, 5,
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
GND
11 (Exposed Pad)
6, 7
8
SW
NC
Switch node. Connect this pin to the inductor.
No internal connection.
Power good indicator. This pin is an open drain logic output. The PGOOD will
be pulled to ground when the output voltage is less than 90% of the target
output voltage.
9
PGOOD
EN
10
Enable control input. Pull high the EN pin to turn on the converter.
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS5771B-01 June 2019
RT5771B
Functional Block Diagram
EN
EN
VIN
ISEN
PGOOD
PGOOD
Slope
Com
OSC
V
REF
0.6V
Output
Clamp
OC
Limit
EA
FB
Driver
Int-SS
SW
Control
Logic
0.54V
NISEN
PGOOD
GND
Current Limit
OTP
0.2V
POR
VCC
UV
Operation
The RT5771B is a synchronous low voltage Buck Converter
that can support the input voltage range from 2.7V to 5.5V
and the output current can be up to 3A. The RT5771B
uses a constant frequency, current mode architecture. In
normal operation, the high-side P-MOSFET is turned on
when the Switch Controller is set by the oscillator (OSC)
and is turned off when the current comparator resets the
switch controller. High-side MOSFET peak current is
measured by internal RSENSE. The Current Signal is where
Slope Compensator works together with sensing voltage
of RSENSE. The error amplifier EA adjusts COMP voltage
by comparing the feedback signal (VFB) from the output
voltage with the internal 0.6V reference. When the load
current increases, it causes a drop in the feedback voltage
relative to the reference, the COMP voltage then rises to
allow higher inductor current to match the load current.
Oscillator (OSC)
The internal oscillator runs at nominal frequency 1MHz.
PGOOD Comparator
When the feedback voltage (VFB) is higher than threshold
voltage 0.54V, the PGOODopen drain output will be high
impedance.
Enable
There is an internal pull down 500kΩ resistor at EN pin.
When the ENpin is higher than 1.6V, the converter will be
turned on. The ENpin can be connected to VINthrough a
100kΩ resistor for automatic startup.
Soft-Start (SS)
An internal current source charges an internal capacitor
to build the soft-start ramp voltage. The VFB voltage will
track the internal ramp voltage during soft-start interval.
The typical soft-start time is 700μs.
UV Comparator
If the feedback voltage (VFB) is lower than threshold voltage
0.2V, the UV Comparator's output will go high and the
Switch Controller will turn off the high-side MOSFET.
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS5771B-01 June 2019
www.richtek.com
3
RT5771B
Absolute Maximum Ratings (Note 1)
Supply Input Voltage, VIN, VCC -------------------------------------------------------------------------------- −0.3V to 6.5V
SW to GND
DC---------------------------------------------------------------------------------------------------------------------- −0.3V to (VIN + 0.3V)
< 100ns --------------------------------------------------------------------------------------------------------------- −2.5V to 9V
Other Pins------------------------------------------------------------------------------------------------------------ −0.3V to 6.5V
Power Dissipation, PD @ TA = 25°C
WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------ 1.429W
Package Thermal Resistance (Note 2)
WDFN-10L 3x3, θJA ------------------------------------------------------------------------------------------------ 70°C/W
WDFN-10L 3x3, θJC ------------------------------------------------------------------------------------------------ 8.2°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
Recommended Operating Conditions (Note 4)
Supply Input Voltage, VIN, VCC -------------------------------------------------------------------------------- 2.7V to 5.5V
Junction Temperature Range------------------------------------------------------------------------------------- −10°C to 105°C
Electrical Characteristics
(VIN = 5.5V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
VREF
Test Conditions
Min
Typ
Max
Unit
V
Feedback Reference Voltage
Feedback Leakage Current
0.594
--
0.6
0.1
110
--
0.606
0.4
170
1
IFB
A
Active , VFB = 0.7V, not switching
Shutdown
--
DC Bias Current
A
--
Output Voltage Line Regulation
Output Voltage Load Regulation
Switch Leakage Current
VIN = 2.7V to 5.5V, IOUT = 0A
(Note 5)
--
0.3
--
--
%/V
%
1
--
1
--
1
A
Switching Frequency
0.8
--
1
1.2
--
MHz
RDS(ON)_P
RDS(ON)_N
ILIM
High-Side
Low-Side
69
49
Switch
On-Resistance
m
--
--
P-MOSFET Current Limit
4.8
2.2
2
--
2.4
2.2
--
--
2.6
2.4
--
A
V
VCC rising
VCC falling
Under-Voltage Lockout
Threshold
VUVLO
Logic-High VIH
1.6
--
EN Input Voltage
V
Logic-Low
VIL
--
0.4
--
EN Pull Low Resistance
--
500
150
k
C
Over-Temperature Protection
TSD
--
--
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS5771B-01 June 2019
RT5771B
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Over-Temperature Protection
Hysteresis
--
20
--
C
Soft-Start Time
tSS
--
--
700
100
--
--
s
VOUT Discharge Resistance
VOUT Under-Voltage Protection
(Latch-Off)
--
33
40
%
Measures FB, with respect to
VREF
Power Good
85
--
90
5
--
--
%
%
Power Good Hysteresis
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 under natural convection (still air) at TA = 25°C with the component mounted on a high effective-
thermal-conductivity four-layer test board on a JEDEC 51-7 thermal measurement standard. 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.
Note 5. Guaranteed by design.
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS5771B-01 June 2019
www.richtek.com
5
RT5771B
Typical Operating Characteristics
Output Voltage vs. Output Current
Efficiency vs. Output Current
1.07
1.06
1.05
1.04
1.03
1.02
1.01
100
90
80
70
VIN = 5V, VOUT = 3.3V
VIN = 3.3V, VOUT = 1.05V
VIN = 5V, VOUT = 1.05V
60
50
40
30
20
10
0
VIN = 5V
VIN = 3.3V
IOUT = 0A to 3A
10
VOUT = 1.05V, IOUT = 0A to 3A
0
0.5
1
1.5
2
2.5
3
0.001
0.01
0.1
1
Output Current (A)
Output Current (A)
Output Voltage vs. Output Current
Switching Frequency vs. Temperature
3.34
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
3.33
3.32
3.31
3.30
3.29
3.28
VIN = 3.3V
VIN = 5V
VIN = 5V, VOUT = 3.3V, IOUT = 0A to 3A
VOUT = 1.05V, IOUT = 0.6A
0
0.5
1
1.5
2
2.5
3
-50
-25
0
25
50
75
100
125
Temperature (°C)
Output Current (A)
Switching Frequency vs. Temperature
Reference Voltage vs. Temperature
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.65
0.64
0.63
0.62
0.61
0.60
0.59
0.58
0.57
0.56
0.55
VIN = 5V, VOUT = 3.3V, IOUT = 0.6A
IOUT = 0.6A
75 100 125
-50
-25
0
25
50
75
100
125
-50
-25
0
25
50
Temperature (°C)
Temperature (°C)
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
6
DS5771B-01 June 2019
RT5771B
UVLO Threshold vs. Temperature
EN Threshold Voltage vs. Temperature
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
Rising
Falling
Rising
Falling
-50
-25
0
25
50
75
100
125
-50
-25
0
25
50
75
100
125
Temperature (°C)
Temperature (°C)
Load Transient Response
Load Transient Response
VOUT
(50mV/Div)
VOUT
(100mV/Div)
IOUT
(2A/Div)
IOUT
(2A/Div)
VIN = 5V, VOUT = 3.3V, IOUT = 1A to 4A
VIN = 5V, VOUT = 1.05V, IOUT = 1A to 4A
Time (100μs/Div)
Time (100μs/Div)
Output Ripple Voltage
Output Ripple Voltage
VOUT
(10mV/Div)
VOUT
(10mV/Div)
VSW
(5V/Div)
VSW
(5V/Div)
VIN = 5V, VOUT = 3.3V, IOUT = 4A
Time (500ns/Div)
VIN = 5V, VOUT = 1.05V, IOUT = 4A
Time (500ns/Div)
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS5771B-01 June 2019
www.richtek.com
7
RT5771B
Power On from VIN
Power Off from VIN
VIN
(5V/Div)
VIN
(5V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
VPGOOD
(10V/Div)
VPGOOD
(10V/Div)
IOUT
(5A/Div)
IOUT
(5A/Div)
VIN = 5V, VOUT = 1.05V, IOUT = 4A
Time (2.5ms/Div)
VIN = 5V, VOUT = 1.05V, IOUT = 4A
Time (5ms/Div)
Power On from VIN
Power Off from VIN
VIN
(5V/Div)
VIN
(5V/Div)
VOUT
(5V/Div)
VOUT
(5V/Div)
VPGOOD
(10V/Div)
VPGOOD
(10V/Div)
IOUT
(5A/Div)
IOUT
(5A/Div)
VIN = 5V, VOUT = 3.3V, IOUT = 4A
Time (2.5ms/Div)
VIN = 5V, VOUT = 3.3V, IOUT = 4A
Time (5ms/Div)
Power On from EN
Power Off from EN
VEN
(5V/Div)
VEN
(5V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
VPGOOD
(5V/Div)
VPGOOD
(5V/Div)
IOUT
(5A/Div)
IOUT
(5A/Div)
VIN = 5V, VOUT = 1.05V, IOUT = 4A
VIN = 5V, VOUT = 1.05V, IOUT = 4A
Time (500μs/Div)
Time (500μs/Div)
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
8
DS5771B-01 June 2019
RT5771B
Power Off from EN
Power On from EN
VEN
(5V/Div)
VEN
(5V/Div)
VOUT
(2V/Div)
VOUT
(2V/Div)
VPGOOD
(5V/Div)
VPGOOD
(5V/Div)
IOUT
(5A/Div)
IOUT
(5A/Div)
VIN = 5V, VOUT = 3.3V, IOUT = 4A
VIN = 5V, VOUT = 3.3V, IOUT = 4A
Time (500μs/Div)
Time (500μs/Div)
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS5771B-01 June 2019
www.richtek.com
9
RT5771B
Application Information
reduce the output surge current. The internal 0.6V
reference takes over the loop control once the internal
ramping-up voltage becomes higher than 0.6V.
The RT5771B is a single-phase step-down converter. It
provides single feedback loop, current mode control with
fast transient response. An internal 0.6V reference allows
the output voltage to be precisely regulated for low output
voltage applications. Afixed switching frequency (1MHz)
oscillator and internal compensation are integrated to
minimize external component count. Protection features
include over-current protection, under-voltage protection
and over-temperature protection.
UVLO Protection
The RT5771B has input under-voltage lockout protection
(UVLO). If the input voltage exceeds the UVLO rising
threshold voltage (2.4V typ.), the converter resets and
prepares the PWM for operation. If the input voltage falls
below the UVLO falling threshold voltage during normal
operation, the device will stop switching. The UVLO rising
and falling threshold voltage has a hysteresis to prevent
noise-caused reset. The power sequence of the VCC and
VINneed to be considered if they are powered separately.
The driver voltage of high-side MOSET comes from VIN
input and internal control circuit is powered by VCC. The
VCC has to be powered earlier than the VIN to ensure
that the high-side MOSFET has never turned on before
the internal control circuit is ready.At power off, the voltage
at the VINhas to be removed before the VCC goes below
the threshold of UVLO.
Output Voltage Setting
Connect a resistive voltage divider at the FB between VOUT
andGNDto adjust the output voltage. The output voltage
is set according to the following equation :
R1
R2
VOUT = VREF 1
where VREF is the feedback reference voltage 0.6V (typ.).
V
OUT
R1
FB
R2
Inductor Selection
GND
The switching frequency (on-time) and operating point (%
ripple or LIR) determine the inductor value as shown below:
Figure 1. Setting VOUT with a Voltage Divider
V
V V
IN OUT
OUT
L =
Chip Enable and Disable
f
LIR I
V
SW
LOAD(MAX) IN
The EN pin allows for power sequencing between the
controller bias voltage and another voltage rail. The
RT5771B remains in shutdown if the ENpin is lower than
400mV. When the EN pin rises above the VEN trip point,
the RT5771B begins a new initialization and soft-start
cycle.
where LIR is the ratio of the peak-to-peak ripple current to
the average inductor current.
Find a low loss inductor having the lowest possible DC
resistance that fits in the allotted dimensions. Ferrite cores
are often the best choice, although powdered iron is
inexpensive and can work well at 200kHz. The core must
be large enough not to saturate at the peak inductor current
(IPEAK) :
Internal Soft-Start
The RT5771B provides an internal soft-start function to
prevent large inrush current and output voltage overshoot
when the converter starts up. The soft-start (SS)
automatically begins once the chip is enabled.During soft-
start, the internal soft-start capacitor becomes charged
and generates a linear ramping up voltage across the
capacitor. This voltage clamps the voltage at the FB pin,
causing PWM pulse width to increase slowly and in turn
LIR
2
IPEAK = ILOAD(MAX)
+
ILOAD(MAX)
The calculation above serves as a general reference. To
further improve transient response, the output inductor
can be further reduced. This relation should be considered
along with the selection of the output capacitor.
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
10
DS5771B-01 June 2019
RT5771B
Input Capacitor Selection
For a given output voltage sag specification, the ESR value
can be determined.
High quality ceramic input decoupling capacitor, such as
X5R or X7R, with values greater than 10μF are
recommended for the input capacitor. The X5R and X7R
ceramic capacitors are usually selected for power regulator
capacitors because the dielectric material has less
capacitance variation and more temperature stability.
Another parameter that has influence on the output voltage
sag is the equivalent series inductance (ESL). The rapid
change in load current results in di/dt during transient.
Therefore, the ESL contributes to part of the voltage sag.
Using a capacitor with low ESL can obtain better transient
performance. Generally, using several capacitors
connected in parallel can have better transient performance
than using a single capacitor for the same total ESR.
Voltage rating and current rating are the key parameters
when selecting an input capacitor. Generally, selecting an
input capacitor with voltage rating 1.5 times greater than
the maximum input voltage is a conservatively safe design.
Unlike the electrolytic capacitor, the ceramic capacitor has
relatively low ESR and can reduce the voltage deviation
during load transient. However, the ceramic capacitor can
only provide low capacitance value. Therefore, use a mixed
combination of electrolytic capacitor and ceramic capacitor
to obtain better transient performance.
The input capacitor is used to supply the input RMS
current, which can be approximately calculated using the
following equation :
V
V
V
OUT
V
IN
OUT
I
= I
1
IN_RMS
LOAD
IN
Power Good Output (PGOOD)
The next step is selecting a proper capacitor for RMS
current rating. One good design is using more than one
capacitor with low equivalent series resistance (ESR) in
parallel to form a capacitor bank.
PGOODis an open-drain type output and requires a pull-
up resistor. PGOOD is actively held low in soft-start,
standby, and shutdown. It is released when the output
voltage rises above 90% of nominal regulation point. The
PGOOD signal goes low if the output is turned off or is
10% below its nominal regulation point.
The input capacitance value determines the input ripple
voltage of the regulator. The input voltage ripple can be
approximately calculated using the following equation :
Under-Voltage Protection (UVP)
IOUT(MAX) 0.25
V
=
IN
The output voltage can be continuously monitored for under
voltage. When under-voltage protection is enabled, both
UGATE and LGATE gate drivers will be forced low if the
output is less than 33% of its set voltage threshold. The
UVP will be ignored for at least 3ms (typ.) after start up or
a rising edge on the ENthreshold. Toggle ENthreshold or
cycle VIN to reset the UVP fault latch and restart the
controller.
CIN fSW
Output Capacitor Selection
The output capacitor and the inductor form a low pass
filter in the Buck topology. In steady state condition, the
ripple current flowing into/out of the capacitor results in
ripple voltage. The output voltage ripple (VP-P) can be
calculated by the following equation :
1
Over-Current Protection (OCP)
VP_P = LIRILOAD(MAX) ESR +
8COUT fSW
The RT5771B provides over-current protection by detecting
high-side MOSFET peak inductor current. If the sensed
peak inductor current is over the current limit threshold,
the OCP will be triggered. When OCP is tripped, the
RT5771B will keep the over current threshold level until
the over current condition is removed.
When load transient occurs, the output capacitor supplies
the load current before the controller can respond.
Therefore, the ESR will dominate the output voltage sag
during load transient. The output voltage undershoot (VSAG
)
can be calculated by the following equation :
VSAG = ILOAD ESR
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS5771B-01 June 2019
www.richtek.com
11
RT5771B
Thermal Shutdown (OTP)
conductivity four-layer test board. The maximum power
dissipation at TA = 25°C can be calculated as below :
The device implements an internal thermal shutdown
function when the junction temperature exceeds 150°C.
The thermal shutdown forces the device to stop switching
when the junction temperature exceeds the thermal
shutdown threshold. Once the die temperature decreases
below the hysteresis of 20°C, the device reinstates the
power up sequence.
PD(MAX) = (125°C − 25°C) / (70°C/W) = 1.429W for a
WDFN-10L 3x3 package.
The maximum power dissipation depends on the operating
ambient temperature for the fixed TJ(MAX) and the thermal
resistance, θJA. The derating curves in Figure 2 allows
the designer to see the effect of rising ambient temperature
on the maximum power dissipation.
Thermal Considerations
The junction temperature should never exceed the
absolute maximum junction temperature TJ(MAX), listed
under Absolute Maximum Ratings, to avoid permanent
damage to the device. The maximum allowable power
dissipation depends on the thermal resistance of the IC
package, the PCB layout, the rate of surrounding airflow,
and the difference between the junction and ambient
temperatures. The maximum power dissipation can be
calculated using the following formula :
Layout Considerations
Layout is very important in high frequency switching
converter design. The PCB can radiate excessive noise
and contribute to converter instability with improper layout.
Certain points must be considered before starting a layout
using the RT5771B.
Make the traces of the main current paths as short and
wide as possible.
Put the input capacitor as close as possible to the device
PD(MAX) = (TJ(MAX) − TA) / θJA
pins (VIN andGND).
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction-to-ambient
thermal resistance.
SW node encounters high frequency voltage swings so
it should be kept in a small area. Keep sensitive
components away from the SW node to prevent stray
capacitive noise pick-up.
For continuous operation, the maximum operating junction
temperature indicated under Recommended Operating
Conditions is 125°C. The junction-to-ambient thermal
resistance, θJA, is highly package dependent. For a
WDFN-10L 3x3 package, the thermal resistance, θJA, is
70°C/W on a standard JEDEC 51-7 high effective-thermal-
Ensure all feedback network connections are short and
direct. Place the feedback network as close to the chip
as possible.
TheGNDpin and Exposed Pad should be connected to
a strong ground plane for heat sinking and noise
protection.
1.5
1.4
Four-Layer PCB
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
An example of PCB layout guide is shown in Figure 3
for reference.
SW should be connected to
inductor by wide and short trace.
Keep sensitive components away
from this trace.
The voltage divider must
be connected as close to
the device as possible.
R1
V
OUT
R2
R
EN
1
2
3
4
5
10
9
EN
PGOOD
NC
SW
FB
VCC
VIN
GND
GND
C
V
IN
IN2
R
PGOOD
L
8
C
IN1
7
V
OUT
11
6
SW
C
OUT
GND
0
25
50
75
100
125
Input capacitor must be placed
as close to the IC as possible.
The output capacitor must
be placed near the IC.
Ambient Temperature (°C)
Figure 2.Derating Curve of Maximum PowerDissipation
Figure 3. PCB Layout Guide
Copyright 2019 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
12
DS5771B-01 June 2019
RT5771B
Outline Dimension
D2
D
L
E
E2
SEE DETAIL A
1
e
b
2
1
2
1
A
A3
DETAILA
Pin #1 ID and Tie Bar Mark Options
A1
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
0.800
0.050
0.250
0.300
3.050
2.650
3.050
1.750
Min
Max
A
A1
A3
b
0.700
0.000
0.175
0.180
2.950
2.300
2.950
1.500
0.028
0.000
0.007
0.007
0.116
0.091
0.116
0.059
0.031
0.002
0.010
0.012
0.120
0.104
0.120
0.069
D
D2
E
E2
e
0.500
0.020
L
0.350
0.450
0.014
0.018
W-Type 10L DFN 3x3 Package
Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Customers should obtain the latest relevant information and data sheets before placing orders and should verify
that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek
product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use;
nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent
or patent rights of Richtek or its subsidiaries.
DS5771B-01 June 2019
www.richtek.com
13
©2020 ICPDF网 联系我们和版权申明