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RT7275/76
3A, 18V, 700kHz ACOT
TM
Synchronous Step-Down Converter
General Description
The RT7275/76 are high-performance 700kHz 3A step-
down regulators with internal power switches and
synchronous rectifiers. They feature quick transient
response using their Advanced Constant On-Time
(ACOT
TM
) control architecture that provides stable
operation with small ceramic output capacitors and without
complicated external compensation, among other benefits.
The input voltage range is from 4.5V to 18V and the output
is adjustable from 0.765V to 8V.
The proprietary ACOT
TM
control improves upon other fast-
response constant on-time architectures, achieving nearly
constant switching frequency over line, load, and output
voltage ranges. Since there is no internal clock, response
to transients is nearly instantaneous and inductor current
can ramp quickly to maintain output regulation without
large bulk output capacitance. The RT7275/76 are stable
with and optimized for ceramic output capacitors.
With internal 90mΩ switches and 60mΩ synchronous
rectifiers, the RT7275/76 display excellent efficiency and
good behavior across a range of applications, especially
for low output voltages and low duty cycles. Cycle-by-
cycle current limit, input under-voltage lock-out,
externally-adjustable soft-start, output under- and over-
voltage protection, and thermal shutdown provide safe and
smooth operation in all operating conditions.
The RT7275 and RT7276 are each available in WDFN-10L
3x3 and PTSSOP-14 packages, with exposed thermal
pads.
Features
Fast Transient Response
Steady 700kHz Switching Frequency
½
At all Load Currents (RT7275)
½
Discontinuous Operating Mode at Light Load
(RT7276)
3A Output Current
Advanced Constant On-Time (ACOT
TM
) Control
Optimized for Ceramic Output Capacitors
4.5V to 18V Input Voltage Range
Internal 90mΩ Switch and 60mΩ Synchronous
Ω
Ω
Rectifier
0.765V to 8V Adjustable Output Voltage
Externally-Adjustable, Pre-Biased Compatible Soft-
Start
Cycle-by-Cycle Current Limit
Optional Output Discharge Function (PTSSOP-14
Only)
Output Over- and Under-Voltage Shut-Down
Applications
Industrial and Commercial Low Power Systems
Computer Peripherals
LCD Monitors and TVs
Green Electronics/Appliances
Point of Load Regulation for High-Performance DSPs,
FPGAs, and ASICs
Not Recommended for Sink/Source Applications
Fast-Transient Response
RT7275
Simplified Application Circuit
V
IN
Input Signal
Power Good
RT7275/76
VIN
SW
VINR
EN
BOOT
FB
V
OUT
V
OUT
(20mV/Div)
PGOOD
VOUT
PVCC
SS
PGND GND
I
OUT
(2A/Div)
V
IN
= 12V, V
OUT
= 1.05V, I
OUT
= 0 to 3A
Time (100μs/Div)
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7275/76-04 April 2017
www.richtek.com
1
RT7275/76
Ordering Information
RT7275/76
Package Type
CP : TSSOP-14 (Exposed Pad)
QW : WDFN-10L 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Operating Mode
75 : Continuous Switching Mode
76 : Discontinuous Operating Mode
at Light Load
Note :
Richtek products are :
½
Pin Configuration
(TOP VIEW)
VOUT
FB
PVCC
SS
GND
PGOOD
EN
14
2
3
4
5
6
7
15
13
12
PGND
11
10
9
8
VINR
VIN
BOOT
SW
SW
PGND
PGND
TSSOP-14 (Exposed Pad)
EN
FB
PVCC
SS
PGOOD
VIN
VIN
BOOT
SW
SW
ments of IPC/JEDEC J-STD-020.
½
Suitable for use in SnPb or Pb-free soldering processes.
WDFN-10L 3x3
Marking Information
RT7275GCP
RT7275GCP : Product Number
RT7276GCP
RT7276GCP : Product Number
YMDNN : Date Code
RT7275
GCPYMDNN
RT7276
GCPYMDNN
YMDNN : Date Code
RT7275GQW
4C= : Product Code
RT7276GQW
2C= : Product Code
YMDNN : Date Code
4C=YM
DNN
2C=YM
DNN
YMDNN : Date Code
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS7275/76-04 April 2017
9
RoHS compliant and compatible with the current require-
1
2
3
4
5
11
10
9
8
7
PGND
RT7275/76
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage, VIN, VINR (TSSOP-14 (Exposed Pad)) -----------------------------------------
−0.3V
to 21V
Switch Node, SW -------------------------------------------------------------------------------------------------
−0.8V
to (V
VIN
+ 0.3V)
Switch Node, SW (<10ns) ---------------------------------------------------------------------------------------
−5V
to 25V
BOOT to SW -------------------------------------------------------------------------------------------------------
−0.3V
to 6V
PVCC ----------------------------------------------------------------------------------------------------------------
−0.3V
to 6V
PVCC to VIN (WDFN-10L 3x3) or VINR (TSSOP-14 (Exposed Pad)) ---------------------------------
−18V
to 0.3V
Other Pins -----------------------------------------------------------------------------------------------------------
−0.3V
to 21V
Power Dissipation, P
D
@ T
A
= 25°C
TSSOP-14 (Exposed Pad) -------------------------------------------------------------------------------------- 2.50W
WDFN-10L 3x3 ----------------------------------------------------------------------------------------------------- 1.67W
Package Thermal Resistance (Note 2)
TSSOP-14 (Exposed Pad),
θ
JA
-------------------------------------------------------------------------------- 40°C/W
WDFN-10L 3x3,
θ
JA
----------------------------------------------------------------------------------------------- 60°C/W
WDFN-10L 3x3,
θ
JC
----------------------------------------------------------------------------------------------- 7.5°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)
HBM (Human Body Model) -------------------------------------------------------------------------------------- 2kV
(Note 4)
Recommended Operating Conditions
Supply Input Voltage, VIN --------------------------------------------------------------------------------------- 4.5V to 18V
Junction Temperature Range ------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
(V
IN
= 12V, T
A
= 25°C, unless otherwise specified)
Parameter
Supply Current
Supply Current (Shutdown)
Supply Current (Quiescent)
Logic Threshold
EN Voltage
Logic High
Logic Low
Symbol
Test Conditions
V
EN
= 0V
V
EN
= 3V, V
FB
= 1V
Min
--
--
1.2
0.4
Typ
1
0.7
1.5
1.3
Max
10
--
2
1.7
Unit
A
mA
V
IH
V
IL
V
FB_TH
I
FB
R
DIS
V
PVCC
4.5V
V
IN
18V
V
FB
= 0.8V
V
EN
= 0V, V
VOUT
= 0.5V
6V
V
IN
18V, 0 < I
PVCC
5mA
6V
V
IN
18V, I
PVCC
= 5mA
V
V
FB
Voltage and Discharge Resistance
Feedback Threshold Voltage
Feedback Input Current
VOUT Discharge Resistance
PVCC Output
PVCC Output Voltage
PVCC Line Regulation
4.7
--
5.1
--
5.5
20
V
mV
0.757
0.1
--
0.765 0.773
0
50
0.1
100
V
A
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7275/76-04 April 2017
www.richtek.com
3
RT7275/76
Parameter
PVCC Load Regulation
Output Current
On-Resistance (R
DS(ON)
)
Switch On
Resistance
High-Side
High-Side
Low-Side
R
DS(ON) _H
R
DS(ON) _H
R
DS(ON) _L
V
IN
= 12V, V
EN
= 0V
L
SW
= 1.4H
For WDFN-10L 3x3
For TSSOP-14 (Exposed Pad)
--
--
--
--
3.5
--
--
V
IN
= 12V, V
OUT
= 1.05V
--
--
--
V
SS
= 0V
V
SS
= 0.5V
V
VIN
/ V
VINR
rising, enable PVCC
regulator
Threshold hysteresis
Power Good
PGOOD Threshold
PGOOD Sink Current
OVP Trip Threshold
OVP Delay Time
UVP Trip Threshold
UVP Delay Time
V
FB
falling
Hysteresis
V
FB
rising
V
FB
falling
PGOOD = 0.5V
V
FB
rising
85
--
--
115
--
65
--
--
90
85
5
120
5
70
10
250
95
--
--
125
--
75
--
--
%
mA
%
s
%
s
1.4
0.05
90
100
60
--
4.5
150
20
145
60
230
2
0.1
--
--
--
1
5.7
--
--
--
--
--
2.6
--
A
A
C
C
ns
ns
ns
A
mA
m
I
PVCC
Symbol
Test Conditions
0
I
PVCC
50mA
V
IN
= 6V, V
PVCC
= 4V
Min
--
--
Typ
--
110
Max
40
--
Unit
mV
mA
High-Side Leakage
Current Limit (upper threshold) I
LIM
Thermal Shutdown
Thermal Shutdown Threshold
T
SD
Thermal Shutdown Hysteresis
T
SD
On-Time and Off-Time Control
On-Time
Minimum On-Time
Minimum Off-Time
Soft-Start
SS Charge Current
SS Discharge Current
VIN UVLO
UVLO Threshold
t
ON
t
ON(MIN)
t
OFF(MIN)
3.55
--
3.85
0.3
4.15
--
V
Output Under-Voltage and Over-Voltage Protection
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
JA
is measured at T
A
= 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7.
θ
JC
is
measured at the exposed pad of the package. The PCB copper area of exposed pad is 70mm
2
.
Note 3.
Devices are ESD sensitive. Handling precaution is recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS7275/76-04 April 2017
RT7275/76
Typical Operating Characteristics
Efficiency vs. Load Current
100
90
80
Efficiency vs. Load Current
100
90
80
RT7275
RT7276
Efficiency (%)
Efficiency (%)
70
60
50
40
30
20
10
0
0.001
0.01
0.1
V
OUT
= 5V
V
OUT
= 2.5V
V
OUT
= 1.05V
70
60
50
40
30
20
V
OUT
= 5V
V
OUT
= 2.5V
V
OUT
= 1.05V
V
IN
= 12V
1
10
10
0
0.001
0.01
0.1
1
V
IN
= 12V
10
Load Current (A)
Load Current (A)
Output Voltage vs. Load Current
1.048
Output Voltage vs. Load Current
1.09
1.08
RT7275
V
IN
= 17V
V
IN
= 12V
RT7276
1.046
Output Voltage (V)
Output Voltage (V)
1.07
1.06
1.05
1.04
1.03
1.02
V
IN
= 17V
V
IN
= 12V
1.044
1.042
V
IN
= 5V
V
IN
= 5V
1.040
V
OUT
= 1.05V
1.038
0
0.5
1
1.5
2
2.5
3
1.01
0
0.5
1
1.5
2
V
OUT
= 1.05V
2.5
3
Load Current (A)
Load Current (A)
Switching Frequency vs. Load Current
800
Switching Frequency vs. Output Current
900
Switching Frequency (kHz)
1
RT7275
RT7276
Switching Frequency (kHz)
1
800
700
600
500
400
300
200
100
0
0
0.5
1
1.5
2
750
V
IN
= 17V
V
IN
= 12V
V
IN
= 5V
700
V
IN
= 5V
V
IN
= 12V
V
IN
= 17V
650
V
OUT
= 1.05V
600
0
0.5
1
1.5
2
2.5
3
V
OUT
= 1.05V
2.5
3
Output Current (A)
Output Current (A)
Copyright
©
2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7275/76-04 April 2017
www.richtek.com
5
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