®
RT7277
3A, 18V, 700kHz ACOTTM Synchronous Step-Down Converter
General Description
The RT7277 is a synchronous step-down DC/DC converter
with Advanced Constant On-Time (ACOT
TM
) mode control.
It achieves high power density to deliver up to 3A output
current from a 4.5V to 18V input supply. The proprietary
ACOTTM mode offers an optimal transient response over a
wide range of loads and all kinds of ceramic capacitors,
which allows the device to adopt very low ESR output
capacitors for ensuring performance stabilization. In
addition, RT7277 keeps an excellent constant switching
frequency under line and load variation and the integrated
synchronous power switches with the ACOTTM mode
operation provides high efficiency in whole output current
load range. Cycle-by-cycle current limit provides an
accurate protection by a valley detection of low side
MOSFET and external soft-start setting eliminates input
current surge during startup. Protection functions also
include output under voltage protection, output over voltage
protection, and thermal shutdown.
Marking Information
RT7277GSP : Product Number
RT7277
GSPYMDNN
YMDNN : Date Code
Features
zz
ACOTTM Mode Enable s Fa st T ra n sient Respon se
z
zz
zz
z 4.5V to 18V Input Voltage Range
zz
zz
z 3A Output Current
zz
ΩΩ
zz
z 60m
Ω Internal Low Site N-MOSFET
zz
ΩΩ
zz
z Advanced Constant On-Time Control
zz
zz
z Support All Ceramic Capa citors
zz
zz
z Up to 95% Efficiency
zz
zz
z 700kHz Switching Frequency
zz
zz
z Adjustable Output Voltage from 0.765V to 8V
zz
zz
z Adjustable Soft-Start
zz
zz
z Cycle-by-Cycle Current Limit
zz
zz
z Input Under Voltage Lockout
zz
zz
z Thermal Shutdown
zz
zz
z RoHS Compliant and Halogen Free
zz
Applications
z Industrial and Commercial Low Power Systems
z Computer Peripherals
z LCD Monitors and TVs
z Green Electronics/Appliances
z Point of Load Regulation for High-Performance DSPs,
FPGAs, and ASICs
Simplified Application Circuit
RT7277
V
IN
VIN
SW
C1 C2
Chip Enable
EN
SS
BOOT
FB
PVCC
C5
GND
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L1
C6
C4
V
C3
PVCC
R1
R2
C7
V
OUT
1
RT7277
Ordering Information
Pin Configurations
RT7277
Package Type
SP : SOP-8 (Exposed Pad-Option 2)
Lead Plating System
G : Green (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.
Functional Pin Description
Pin No. Pin Name Pin Function
1 EN
2 FB
3 PVCC
4 SS
5, 9
(Exposed Pad)
GND
Enable Input. A logic-high enables the converter; a logic-low forces the IC into
shutdown mode reducing the supply current to less than 10μA.
Feedback Input. It is used to regulate the output of the converter to a set value via
an external resistive voltage divider. The feedback threshold voltage is 0.765V
typically.
Internal Regulator Output. Connect a 1μ F capacitor to GND to stabilize output
voltage.
Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from
SS to GND to set the soft-start period. A 3.9nF capacitor sets the soft-start period of
to 2.6ms.
V
OUT
Ground. The Exposed pad should be soldered to a large PCB and connected to
GND for maximum thermal dissipation.
(TOP VIEW)
EN
FB
PVCC
SS
2
GND
3
4
SOP-8 (Exposed Pad)
8
VIN
7
BOOT
6
9
SW
5
GND
6 SW Switch Node. Connect this pin to an external L-C filter.
7 BOOT
8 VIN
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Bootstrap Supply for High Side Gate Driver. Connect a 0.1μF or greater ceramic
capacitor from BOOT to SW pins.
Power Input. The input voltage range is from 4.5V to 18V. Must bypass with a
suitably large ( ≥10μ F x 2) ceramic capacitor.
DS7277-01 March 2013 www.richtek.com
Function Block Diagram
RT7277
Operation
SS
FB
PVCC
Internal
Regulator
VIBIAS
PVCC
On-Time
2µA
PVCC
V
REF
Ripple
Gen.
Over Current
Protection
Switch
Controller
+
- -
FB
Comparator
BOOT
PVCC
Driver
SW
EN
EN
VIN
UGATE
SW
LGATE
GND
In normal operation, the high side N-MOSFET is turned
on when the FB Comparator sets the Switch Controller,
and it is turned off when On-Time Controller resets the
Switch Controller. While the high side N-MOSFET is turned
off, the low side N-MOSFET is turned on and waits for the
FB Comparator to set the beginning of next cycle.
The FB Comparator sets the Switch Controller by
comparing the feedback signal (FB) from output voltage
with the internal 0.765V reference. When load transient
induces VOUT drop, the FB voltage will be less than its
threshold voltage. This means that the high side N-MOSFET
will turn on again immediately after minimum off-time
expired. The switching frequency will vary during the
transient period thus can provide a very fast transient
response. After the load transient finished, the RT7277
will be back to steady state with a constant switching
frequency.
Enable
Activate internal regulator once EN input level is higher
than the target level. Force IC to enter shutdown mode
when the EN input level is lower than 0.4V
Internal Regulator
Provide internal power for logic control and switch gate
drivers.
On-Time Controller
Control on-time according to VIN and SW to obtain
constant switching frequency.
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3
RT7277
Absolute Maximum Ratings (Note 1)
z Supply Voltage, VIN ----------------------------------------------------------------------------------------------- − 0.3V to 21V
z Switch Voltage, SW ----------------------------------------------------------------------------------------------- − 0.8V to (V
<10ns ----------------------------------------------------------------------------------------------------------------- − 5V to 25V
z BOOT to SW, PVCC ---------------------------------------------------------------------------------------------- − 0.3V to 6V
z Other Pins Voltage ------------------------------------------------------------------------------------------------- − 0.3V to 21V
z Power Dissipation, P
@ TA = 25°C
D
SOP-8 (Exposed Pad) -------------------------------------------------------------------------------------------- 2.041W
z Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad), θ JA--------------------------------------------------------------------------------------- 49° C/W
SOP-8 (Exposed Pad), θ JC-------------------------------------------------------------------------------------- 15° C/W
z Junction Temperature Range------------------------------------------------------------------------------------- 150°C
z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°C
z Storage Temperature Range ------------------------------------------------------------------------------------- − 65° C to 150°C
z ESD Susceptibility (Note 3)
HBM (Human Body Model)--------------------------------------------------------------------------------------- 2kV
+ 0.3V)
IN
Recommended Operating Conditions
z Supply Voltage, VIN ----------------------------------------------------------------------------------------------- 4.5V to 18V
z Junction Temperature Range------------------------------------------------------------------------------------- − 40° C to 125°C
z Ambient Temperature Range------------------------------------------------------------------------------------- − 40° C to 85°C
(Note 4)
Electrical Characteristics
(VIN = 12V, T
Supply Current
Shutdown Current I
Quiescent Current IQ V
Logic Threshold
EN Voltage
VFB Voltage and Discharge Resistance
Feedback Threshold Voltage VFB 4.5V ≤ V
Feedback Input Current IFB V
V
Output
PVCC
V
Output Voltage V
PVCC
Line Regulation 6V ≤ V
Load Regulation 0 < I
Output Current I
= 25° C, unless otherwise specified)
A
Parameter Symbol Test Conditions Min Typ Max Unit
V
SHDN
= 0V -- 1.5 10 μA
EN
= 3V, VFB = 1V -- 0.7 -- mA
EN
Logic-High 2 -- 18
Logic-Low -- -- 0.4
≤ 18V 0.757 0.765 0.773 V
IN
= 0.8V − 0.1 0 0.1 μA
FB
6V ≤ V
PVCC
V
PVCC
IN
≤ 18V, 0 < I
IN
≤ 18V, I
IN
< 5mA -- -- 100 mV
PVCC
= 6V, V
PVCC
= 4V -- 110 -- mA
PVCC
< 5mA 4.7 5.1 5.5 V
PVCC
= 5mA -- -- 20 mV
V
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RT7277
Parameter Symbol Test Conditions Min Typ Max Unit
R
Switch On
Resistance
DS(ON)
High Side
R
DS(ON)_H
-- 90 --
mΩ
Low Side
R
DS(ON)_L
-- 60 --
Current Limit
Current Limit I
3.5 4.1 5.7 A
LIM
Thermal Shutdown
Thermal Shutdown Threshold TSD -- 150 -- °C
Thermal Shutdown Hysteresis ΔT SD -- 20 -- °C
On-Time Timer Control
On-Time tON V
Minimum On-Time t
Minimum Off-Time t
ON(MIN)
OFF(MIN)
-- 60 -- ns
= 12V, V
IN
= 1.05V -- 145 -- ns
OUT
-- 230 -- ns
Soft-Start
SS Charge Current VSS = 0V 1.4 2 2.6 μA
SS Discharge Current VSS = 0.5V 0.05 0.1 -- mA
UVLO
UVLO Threshold VIN Rising to Wake up V
3.55 3.85 4.15
PVCC
V
Hysteresis -- 0.3 --
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. The PCB copper area of exposed pad is 70mm
= 25° C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θ JC is
A
2
.
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RT7277
Typical Application Circuit
V
IN
Chip Enable
V
(V) R1 (kΩ ) R2 (kΩ ) C3 (pF) L1 (μ H) C7 (μ F)
OUT
1 6.81 22.1 -- 1.4 22 to 68
1.05 8.25 22.1 -- 1.4 22 to 68
1.2 12.7 22.1 -- 1.4 22 to 68
1.8 30.1 22.1 5 to 22 2 22 to 68
2.5 49.9 22.1 5 to 22 2 22 to 68
3.3 73.2 22.1 5 to 22 2 22 to 68
5 124 22.1 5 to 22 3.3 22 to 68
7 180 22.1 5 to 22 3.3 22 to 68
C1
10µF x 2
5, 9 (Exposed Pad)
C2
0.1µF
C5
3.9nF
Table 1. Suggested Component Values
8
1
4
VIN
EN
GND
SS
RT7277
BOOT
PVCC
SW
FB
L1
6
7
2
3
1.4µH
C6
0.1µF
C4
1µF
V
PVCC
C3
R1
8.25k
R2
22.1k
C7
22µF x 2
V
OUT
1.05V/3A
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Typical Operating Characteristics
RT7277
Efficiency vs. Output Current
100
90
80
70
60
50
V
= 5V
40
Efficiency (%)
30
20
10
0
0.001 0.01 0.1 1 10
V
V
IN
IN
IN
= 12V
= 17V
Output Current (A)
Output Voltage vs. Temperature
1.065
1.060
1.055
1.050
1.045
1.040
Output Voltage (V)
1.035
V
OUT
= 1.05V
Output Voltage (V)
Output Voltage (V)
Output Voltage vs. Input Voltage
1.065
1.060
1.055
1.050
1.045
1.040
1.035
1.030
1.025
4 6 8 1 01 21 41 61 8
V
OUT
Input Voltage (V)
Output Voltage v s . Output Current
1.065
1.060
1.055
1.050
V
= 17V
1.045
1.040
1.035
V
V
IN
IN
IN
= 12V
= 5V
= 1.05V
1.030
1.025
-50 -25 0 25 50 75 100 125
V
IN
= 12V, V
OUT
= 1.05V, I
OUT
= 0A
Temperature (°C)
Frequency vs. Input Voltage
750
740
730
720
710
700
690
680
Frequency (kHz) 1
670
660
650
4681 01 21 41 61 8
Input Voltage (V)
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Reference Voltage (V)
1.030
1.025
00 . 511 . 522 . 53
V
OUT
Output Current (A)
Reference Voltage vs. Temperature
0.785
0.780
0.775
0.770
0.765
0.760
0.755
0.750
0.745
-50 -25 0 25 50 75 100 125
Temperature (°C)
= 1.05V
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RT7277
Current Limit vs . Te m pe rature
6.0
5.6
5.2
4.8
Current Limit (A)
4.4
V
= 12V, V
IN
4.0
- 5 0- 2 50 2 55 07 51 0 01 2 5
OUT
Temperature (°C)
Load Transient Response
I
OUT
(2A/Div)
= 1.05V
6.0
5.5
5.0
4.5
4.0
Current Limit (A)
3.5
3.0
V
SW
(10V/Div)
V
OUT
(10mV/Div)
Current Limit vs. Input Voltage
V
= 12V, V
IN
4681 01 21 41 61 8
OUT
= 1.05V
Input Voltage (V)
Switching
V
OUT
(20mV/Div)
V
IN
(5V/Div)
V
OUT
(1V/Div)
I
OUT
(2A/Div)
V
= 12V, V
IN
OUT
= 1.05V, I
Time (100μs/Div)
Power On from VIN
V
= 12V, V
IN
Time (5ms/Div)
OUT
= 1.05V, I
= 0A to 3A
OUT
OUT
= 3A
I
L
(2A/Div)
V
IN
(5V/Div)
V
OUT
(1V/Div)
I
OUT
(2A/Div)
V
= 12V, V
IN
OUT
= 1.05V, I
Time (1μs/Div)
Power Off from VIN
V
= 12V, V
IN
Time (10ms/Div)
OUT
= 1.05V, I
OUT
OUT
= 3A
= 3A
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RT7277
V
EN
(2V/Div)
V
OUT
(1V/Div)
I
OUT
(2A/Div)
10
EN Current (μA)
Power On from EN
V
= 12V, V
IN
OUT
= 1.05V, I
OUT
Time (1ms/Div)
EN Current vs. EN Voltage
9
8
7
6
5
4
3
2
1
0
0 2 4 6 8 10 12 14 16 18
EN Voltage (V)
V
IN
= 17V
= 3A
V
EN
(2V/Div)
V
OUT
(1V/Div)
I
OUT
(2A/Div)
Power Off from EN
V
= 12V, V
IN
Time (10μs/Div)
OUT
= 1.05V, I
OUT
= 3A
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RT7277
Application Information
The RT7277 is a synchronous high voltage Buck converter
that can support the input voltage range from 4.5V to 18V
and the output current up to 3A. It adopts ACOTTM mode
control to provide a very fast transient response with few
external compensation components.
PWM Operation
It is suitable for low external component count
configuration with appropriate amount of Equivalent Series
Resistance (ESR) capacitors at the output. The output
ripple valley voltage is monitored at a feedback point
voltage. The synchronous high side MOSFET is turned
on at the beginning of each cycle. After the internal on-
time timer expires, the MOSFET is turned off. The pulse
width of this on-time is determined by the converter's input
and output voltages to keep the frequency fairly constant
over the entire input voltage range.
Advanced Constant On-Time Control
The RT7277 has a unique circuit which sets the on-time
by monitoring the input voltage and SW signal. The circuit
ensures the switching frequency operating at 700kHz over
input voltage range and loading range.
device again. For external timing control, the EN pin can
also be externally pulled high by adding a REN resistor
and CEN capacitor from the VIN pin (see Figure 1).
EN
V
R
IN
EN
C
EN
EN
RT7277
GND
Figure 1. External Timing Control
An external MOSFET can be added to implement digital
control on the EN pin when no system voltage above 2V
is available, as shown in Figure 2. In this case, a 100kΩ
pull-up resistor, REN, is connected between VIN and the
EN pin. MOSFET Q1 will be under logic control to pull
down the EN pin.
R
EN
100k
V
EN
IN
Q1
EN
RT7277
GND
Figure 2. Digital Enable Control Circuit
Soft-Start
The RT7277 contains an external soft-start clamp that
gradually raises the output voltage. The soft-start timing
can be programmed by the external capacitor between
SS pin and GND. The chip provides a 2μ A charge current
for the external capacitor. If a 3.9nF capacitor is used,
the soft-start will be 2.6ms (typ.). The available capacitance
range is from 2.7nF to 220nF.
t ( m s ) =
SS
C5 (nF) 1.365
×
I (A )
μ
SS
Chip Enable Operation
The EN pin is the chip enable input. Pulling the EN pin
low (<0.4V) will shut down the device. During shutdown
mode, the RT7277 quiescent current drops to lower than
10μ A. Driving the EN pin high (>2V, <18V) will turn on the
To prevent enabling circuit when VIN is smaller than the
V
target value, a resistive voltage divider can be placed
OUT
between the input voltage and ground and connected to
the EN pin to adjust IC lockout threshold, as shown in
Figure 3. For example, if an 8V output voltage is regulated
from a 12V input voltage, the resistor R
can be selected
EN2
to set input lockout threshold larger than 8V.
R
V
EN1
IN
R
EN2
EN
RT7277
GND
Figure 3. Resistor Divider for Lockout Threshold Setting
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RT7277
Output Voltage Setting
The resistive divider allows the FB pin to sense the output
voltage as shown in Figure 4.
V
OUT
R1
FB
RT7277
GND
R2
Figure 4. Output Voltage Setting
The output voltage is set by an external resistive divider
according to the following equation. It is recommended to
use 1% tolerance or better divider resistors.
R1
V = 0 . 7 6 5 ( 1
OUT
×+
R2
)
Under Voltage Lockout Protection
The RT7277 has Under Voltage Lockout Protection (UVLO)
that monitors the voltage of PVCC pin. When the V
PVCC
voltage is lower than UVLO threshold voltage, the RT7277
will be turned off in this state. This is non-latch protection.
inductor to achieve this goal. For the ripple current
selection, the value of ΔI L = 0.2(I
) will be a reasonable
MAX
starting point. The largest ripple current occurs at the
highest VIN. To guarantee that the ripple current stays
below the specified maximum, the inductor value should
be chosen according to the following equation :
⎡⎤ ⎡ ⎤
VV
L = 1
OUT OUT
⎢⎥ ⎢ ⎥
fI V
×Δ
L(MAX) IN(MAX)
⎣⎦ ⎣ ⎦
×−
Input and Output Capacitors Selection
The input capacitance, CIN, is needed to filter the
trapezoidal current at the source of the high side MOSFET.
A low ESR input capacitor with larger ripple current rating
should be used for the maximum RMS current. The RMS
current is given by :
V
I = I 1
RMS OUT(MAX)
OUT
VV
This formula has a maximum at VIN = 2V
I
RMS
= I
/ 2. This simple worst-case condition is
OUT
V
IN
IN OUT
−
, where
OUT
commonly used for design because even significant
deviations do not offer much relief.
Over Temperature Protection
The RT7277 equips an Over Temperature Protection (OTP)
circuitry to prevent overheating due to excessive power
dissipation. The OTP will shut down switching operation
when junction temperature exceeds 150° C. Once the
junction temperature cools down by approximately 20°C
the main converter will resume operation. To keep operating
at maximum, the junction temperature should be prevented
from rising above 150°C.
Inductor Selection
The inductor value and operating frequency determine the
ripple current according to a specific input and an output
voltage. The ripple current ΔI L increases with higher V
and decreases with higher inductance.
VV
⎡⎤ ⎡ ⎤
OUT OUT
I = 1
Δ× −
L
⎢⎥ ⎢ ⎥
fL V
×
⎣⎦ ⎣ ⎦
IN
Having a lower ripple current reduces not only the ESR
losses in the output capacitors but also the output voltage
ripple. High frequency with small ripple current can achieve
highest efficiency operation. However, it requires a large
Choose a capacitor rated at a higher temperature than
required. Several capacitors may also be paralleled to
meet size or height requirements in the design. For the
input capacitor, two 10μ F and 0.1μ F low ESR ceramic
capacitors are recommended.
The selection of C
is determined by the required ESR
OUT
to minimize voltage ripple.
Moreover, the amount of bulk capacitance is also a key
for C
The output ripple, ΔV
Δ≤ Δ +
selection to ensure that the control loop is stable.
OUT
, is determined by :
OUT
8fC
1
OUT
VI E S R
OUT L
⎡⎤
⎢⎥
⎣⎦
The output ripple will be highest at the maximum input
IN
voltage since ΔI L increases with input voltage. Multiple
capacitors placed in parallel may need to meet the ESR
and RMS current handling requirements.
Higher values, lower cost ceramic capacitors are now
becoming available in smaller case sizes. Their high ripple
current, high voltage rating and low ESR make them ideal
for switching regulator applications. However, care must
be taken when these capacitors are used at input and
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11
RT7277
output. When a ceramic capacitor is used at the input
and the power is supplied by a wall adapter through long
wires, a load step at the output can induce ringing at the
input, VIN. A sudden inrush of current through the long
wires can potentially cause a voltage spike at VIN large
enough to damage the part.
External Bootstrap Diode
Connect a 0.1μ F low ESR ceramic capacitor between the
BOOT and SW pins. This capacitor provides the gate driver
voltage for the high side MOSFET. It is recommended to
add an external bootstrap diode between an external 5V
and the BOOT pin for efficiency improvement when input
voltage is lower than 5.5V or duty ratio is higher than 65%.
The bootstrap diode can be a low cost one such as 1N4148
or BAT54. The external 5V can be a 5V fixed input from
system or a 5V output of the RT7277. Note that the external
boot voltage must be lower than 5.5V
5V
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
P
where T
the ambient temperature, and θ
D(MAX)
= (T
J(MAX)
− TA) / θ
J(MAX)
JA
is the maximum junction temperature, T
is the junction to ambient
JA
A
thermal resistance.
For recommended operating condition specifications, the
maximum junction temperature is 125° C. The junction to
ambient thermal resistance, θ JA, is layout dependent. For
SOP-8 (Exposed Pad) package, the thermal resistance,
θJA, is 49°C/W on a standard JEDEC 51-7 four-layer
thermal test board. The maximum power dissipation at
TA = 25° C can be calculated by the following formulas :
is
BOOT
RT7277
SW
0.1µF
Figure 5. External Bootstrap Diode
PVCC Capacitor Selection
Decouple with a 1μ F ceramic capacitor. X7R or X5R grade
dielectric ceramic capacitors are recommended for their
stable temperature characteristics.
Over Current Protection
When the output shorts to ground, the inductor current
decays very slowly during a single switching cycle. An
over current detector is used to monitor inductor current
to prevent current runaway. The over current detector
monitors the voltage between SW and GND during the
low side MOS turn-on state. This is cycle-by-cycle
protection. The over current detector also supports
temperature compensated.
P
= (125°C − 25° C) / (49° C/W) = 2.041W for
D(MAX)
SOP-8 (Exposed Pad) package
The maximum power dissipation depends on the operating
ambient temperature for fixed T
and thermal
J(MAX)
resistance, θ JA. The derating curve in Figure 6 allow the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
2.5
2.0
1.5
1.0
0.5
Maximum Power Dissipation (W) 1
0.0
0 25 50 75 100 125
Ambient Temperature (°C)
Four-Layer PCB
Figure 6. Derating Curve of Maximum Power Dissipation
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Layout Consideration
Follow the PCB layout guidelines for optimal performance
of the RT7277
` Keep the traces of the main current paths as short and
wide as possible.
` Put the input capacitor as close as possible to the device
pins (VIN and GND).
RT7277
` SW node is with high frequency voltage swing and
should be kept at small area. Keep sensitive
components away from the SW node to prevent stray
capacitive noise pickup.
` Connect feedback network behind the output capacitors.
Keep the loop area small. Place the feedback
components near the RT7277 feedback pin.
` The GND and Exposed Pad should be connected to a
strong ground plane for heat sinking and noise protection.
The resistor divider must be connected
as close to the device as possible.
V
OUT
GND
R1
R2
C4
C5
EN
FB
PVCC
SS
Input capacitor must be placed
C1
as close to the IC as possible.
C2
8
VIN
2
3
4
GND
7
BOOT
6
9
SW
5
GND
C6
C7
Figure 7. PCB Layout Guide
SW should be connected to inductor by
wide and short trace. Keep sensitive
components away from this trace.
L1
V
OUT
Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
©
DS7277-01 March 2013 www.richtek.com
13
RT7277
Outline Dimension
H
M
EXPOSED THERMAL PAD
(Bottom of Package)
A
Y
J
I
B
X
F
C
D
Dimensions In Millimeters Dime nsions In Inches
Symbol
Min Max Min Max
A 4.801 5.004 0.189 0.197
B 3.810 4.000 0.150 0.157
C 1.346 1.753 0.053 0.069
D 0.330 0.510 0.013 0.020
F 1.194 1.346 0.047 0.053
H 0.170 0.254 0.007 0.010
I 0.000 0.152 0.000 0.006
J 5.791 6.200 0.228 0.244
M 0.406 1.270 0.016 0.050
X 2.000 2.300 0.079 0.091
Option 1
Y 2.000 2.300 0.079 0.091
X 2.100 2.500 0.083 0.098
Option 2
Y 3.000 3.500 0.118 0.138
8-Lead SOP (Exposed Pad) Plastic Package
Richtek Technology Corporation
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. 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.
DS7277-01 March 2013 www.richtek.com
14