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RT7295C
3.5A, 18V, 500kHz ACOT
TM
Synchronous Step-Down Converter
General Description
The RT7295C is a synchronous step-down converter with
Advanced Constant On-Time (ACOT
TM
) mode control. The
ACOT
TM
provides a very fast transient response with few
external components. The low impedance internal
MOSFET supports high efficiency operation with wide input
voltage range from 4.3V to 18V. The proprietary circuit
of
the RT7295C enables to support all ceramic capacitors.
The output voltage can be adjusted between 0.6V and 8V.
Features
4.3V to 18V Input Voltage Range
3.5A Output Current
Advanced Constant On-Time Control
Fast Transient Response
Support All Ceramic Capacitors
Up to 95% Efficiency
500kHz Switching Frequency
Adjustable Output Voltage from 0.6V to 8V
Cycle-by-Cycle Current Limit
Input Under-Voltage Lockout
Hiccup Mode Under-Voltage Protection
Thermal Shutdown
RoHS Compliant and Halogen Free
Ordering Information
RT7295C
Package Type
J6F : TSOT-23-6 (FC)
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.
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
Pin Configurations
(TOP VIEW)
SW VIN EN
Marking Information
05= : Product Code
05=DNN
6
5
4
DNN : Date Code
2
3
BOOT GND FB
TSOT-23-6 (FC)
Simplified Application Circuit
V
IN
RT7295C
BOOT
VIN
SW
V
OUT
Enable
EN
GND
FB
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7295C-09
February 2018
www.richtek.com
1
RT7295C
Functional Pin Description
Pin No.
1
2
3
4
5
6
Pin Name
BOOT
GND
FB
EN
VIN
SW
Pin Function
Bootstrap Supply for High-Side Gate Driver. Connect a 0.1µF ceramic capacitor
between the BOOT and SW pins.
Power Ground.
Feedback Voltage Input. The pin is used to set the output voltage of the converter
via a resistive divider. The converter regulates V
FB
to 0.6V
Enable Control Input. Connect EN to a logic-high voltage to enable the IC or to a
logic-low voltage to disable. Do not leave this high impedance input unconnected.
Power Input. The input voltage range is from 4.3V to 18V. Must bypass with a
suitable large ceramic capacitor at this pin.
Switch Node. Connect to external L-C filter.
Function Block Diagram
BOOT
V
IN
Reg
VIBIAS
PVCC
V
REF
Min off
PVCC
UGATE
Control
UV & OV
PVCC
SW
Ripple
Gen.
+
-
-
Comparator
EN
GND SW
V
IN
On-Time
SW
Driver
LGATE
GND
SW
VIN
OC
FB
EN
Operation
The RT7295C is a synchronous step-down converter with
advanced constant on-time control mode. Using the ACOT
control mode can reduce the output capacitance and fast
transient response. It can minimize the component size
without additional external compensation network.
Current Protection
The inductor current is monitored via the internal switches
cycle-by-cycle. Once the output voltage drops under UV
threshold, the RT7295C will enter hiccup mode.
UVLO Protection
To protect the chip from operating at insufficient supply
voltage, the UVLO is needed. When the input voltage of
VIN is lower than the UVLO falling threshold voltage, the
device will be lockout.
Thermal Shutdown
When the junction temperature exceeds the OTP
threshold value, the IC will shut down the switching
operation. Once the junction temperature cools down and
is lower than the OTP lower threshold, the converter will
autocratically resume switching.
is a registered trademark of Richtek Technology Corporation.
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
DS7295C-09
February 2018
RT7295C
Absolute Maximum Ratings
(Note 1)
−0.3V
to 20V
−0.3V
to (V
IN
+ 0.3V)
−5V
to 25V
(V
SW
−
0.3V) to (V
SW
+ 6V)
−0.3V
to 6V
VIN to GND -----------------------------------------------------------------------------------------------------
SW to GND ----------------------------------------------------------------------------------------------------
< 10ns -----------------------------------------------------------------------------------------------------------
BOOT to GND -------------------------------------------------------------------------------------------------
Other Pins ------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
TSOT-23-6 (FC) ----------------------------------------------------------------------------------------------- 1.429W
Package Thermal Resistance (Note 2)
TSOT-23-6 (FC),
θ
JA
------------------------------------------------------------------------------------------ 70°C/W
TSOT-23-6 (FC),
θ
JC
----------------------------------------------------------------------------------------- 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
Recommended Operating Conditions
(Note 4)
Supply Input Voltage, VIN ---------------------------------------------------------------------------------- 4.3V 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
Shutdown Current
Quiescent Current
Switch-On Resistance
Current Limit
Oscillator Frequency
Maximum Duty Cycle
Minimum On-Time
Feedback Threshold Voltage
EN Input Threshold
High-Side
Low-Side
Symbol
I
SHDN
I
Q
R
DS(ON)_H
R
DS(ON)_L
I
LIM
f
SW
D
MAX
t
ON
V
FB
V
EN_L
V
UVLO
Test Conditions
V
EN
= 0V
V
EN
= 2V, V
FB
= 1V
V
BOOT−SW
= 4.8V
V
IN
= 5V
Valley Current
Min
--
--
--
--
3.7
--
--
--
Typ
--
0.5
90
45
4.4
500
90
60
600
1.29
1.03
3.9
340
Max
4
--
105
65
5
--
--
--
609
1.39
1.13
4.25
--
Unit
µA
mA
mΩ
A
kHz
%
ns
mV
V
V
mV
In CCM Mode
591
1.19
0.93
Logic-High V
EN_H
Logic-Low
VIN Under-Voltage Lockout
Threshold
VIN Under-Voltage Lockout
Threshold Hysteresis
V
IN
Rising
3.55
--
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7295C-09
February 2018
www.richtek.com
3
RT7295C
Parameter
Soft-Start Time
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
V
OUT
Discharge Resistance
Output Under-Voltage Trip
Threshold
Output Under-Voltage Delay
Time
t
SS
T
SD
∆T
SD
R
DISCHG
EN = 0V, V
OUT
= 0.5V
UVP Detect
Hysteresis
Symbol
Test Conditions
Min
--
--
--
--
70
--
--
Typ
800
160
20
50
75
10
250
Max
--
--
--
100
80
--
--
Unit
µs
°C
°C
Ω
%
µs
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. The first
layer of copper area is filled.
θ
JC
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
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS7295C-09
February 2018
RT7295C
Typical Application Circuit
RT7295C
V
IN
4.3V to 18V
5
C
IN
10µF
VIN
BOOT
1
C
BOOT
100nF
L
2µH
C
FF
Enable
4 EN
FB 3
GND 2
R1
10k
R2
10k
V
OUT
1.2V
C
OUT
22µF x 2
SW 6
Table 1. Suggested Component Values
V
OUT
(V)
5
3.3
2.5
1.2
R1 (kΩ)
110
115
25.5
10
R2 (kΩ)
15
25.5
8.06
10
L (µH)
4.7
3.6
3.6
2
C
OUT
(µF)
22 x 2
22 x 2
22 x 2
22 x 2
C
FF
(pF)
39
33
NC
NC
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7295C-09
February 2018
www.richtek.com
5
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