RT8097B
2A, 1MHz, 6V CMCOT Synchronous Step-Down Converter
General Description
The RT8097B is a high efficiency synchronous step-
down DC-DC converter. Its input voltage range is from
2.7V to 6V and provides an adjustable regulated output
voltage from 0.6V to 3.4V while delivering up to 2A of
output current.
The internal synchronous low on-resistance power
switches increase efficiency and eliminate the need for
an external Schottky diode. The Current Mode
Constant-On-time (CMCOT) operation with internal
compensation allows the transient response to be
optimized over a wide range of loads and output
capacitors. The RT8097B is available in the SOT-23-5/6
package.
Features
Efficiency Up to 95%
R
DSON
100m HS / 70m LS
V
IN
Range 2.7V to 6V
V
REF
0.6V with
1.5%
Accuracy at 25C
CMCOT
™
Control Loop Design for
Best
Transient Response, Robust Loop Stability with
Low-ESR (MLCC) C
OUT
Soft-Start 1.2ms; PGOOD Function in SOT-23-6
Applications
STB, Cable Modem, & xDSL Platforms
LCD TV Power Supply & Metering Platforms
General Purpose Point of Load (POL)
Ordering Information
RT8097B
Package Type
B : SOT-23-5
E : SOT-23-6
Lead Plating System
G : Green (Halogen Free and Pb Free)
UVP Option
H : Hiccup
L : Latched-Off
B : Forced PWM
Note :
Richtek products are :
Pin Configuration
(TOP VIEW)
FB
5
VIN
4
FB
6
PG VIN
5
4
2
3
2
3
EN GND LX
EN GND LX
SOT-23-5
SOT-23-6
RoHS compliant and compatible with the current
requirements of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Simplified Application Circuit
RT8097B
LX
VIN
C
IN
EN
PG*
GND
FB
R2
L
V
OUT
R1
C
OUT
V
IN
*For SOT-23-6 Package Only
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8097B-06
March 2017
www.richtek.com
1
RT8097B
Marking Information
RT8097BHGB
RT8097BHGE
4L= : Product Code
DNN : Date Code
1T= : Product Code
DNN : Date Code
4L=DNN
RT8097BLGB
1T=DNN
RT8097BLGE
4K=DNN
4K= : Product Code
DNN : Date Code
1S=DNN
1S= : Product Code
DNN : Date Code
Functional Pin Description
Pin No.
SOT-23-5
1
2
3
4
5
SOT-23-6
1
2
3
4
6
Pin Name
EN
GND
LX
VIN
FB
Enable Control Input.
Power Ground.
Switch Node.
Supply Voltage Input. The RT8097B operates from a 2.7V to 6V input.
Feedback Voltage Input. An external resistor divider from the output to
GND, tapped to the FB pin, sets the output voltage.
Power Good Indicator. The output of this pin is an open-drain with
external pull-up resistor. PG is pulled up when the FB voltage is within
90%, otherwise it is LOW.
Pin Function
--
5
PG
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8097B-06
March 2017
RT8097B
Functional Block Diagram
For SOT-23-5 Package
EN
VIN
UVLO
OTP
FB
V
REF
Shut Down
Control
Error
Amplifier
R
C
C
COMP
Comparator
+
-
Ton
LX
VIN
-
+
Logic
Control
Current
Limit
Detector
Current
Sense
Driver
LX
GND
LX
For SOT-23-6 Package
EN
VIN
UVLO
OTP
FB
V
REF
-
+
Shut Down
Control
Error
Amplifier
R
C
C
COMP
Comparator
+
-
Ton
LX
VIN
Logic
Control
Current
Limit
Detector
Current
Sense
Driver
LX
GND
+
-
LX
PG
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8097B-06
March 2017
www.richtek.com
3
RT8097B
Operation
The RT8097B is a synchronous low voltage step-down
converter that can support the input voltage range from
2.7V to 6V and the output current can be up to 2A. The
RT8097B uses a constant on-time, current mode
architecture. In normal operation, the high side P-
MOSFET is turned on when the switch controller is set
by the comparator and is turned off when the Ton
comparator resets the switch controller.
Low side MOSFET peak current is measured by internal
RSENSE. The error amplifier EA adjusts COMP voltage
by comparing the feedback signal (V
FB
) 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, then the COMP
voltage rises to allow higher inductor current to match
the load current.
UV Comparator
If the feedback voltage (V
FB
) 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. The output under voltage protection is
designed to operate in Hiccup mode for RT8097BH,
Latch mode for RT8097BL.
PGOOD Comparator
When the feedback voltage (V
FB
) is higher than
threshold voltage 0.54V, the PGOOD open drain output
will be high impedance. The internal PG MOSFET is
typical 10. The PGOOD signal delay time from EN is
about 2ms.
Enable Comparator
A logic-high enables the converter; a logic-low forces
the IC into shutdown mode.
Soft-Start (SS)
An internal current source charges an internal capacitor
to build the soft-start ramp voltage. The V
FB
voltage will
track the internal ramp voltage during soft-start interval.
The typical soft-start time is 1.2ms.
Over Current Protection (OCP)
The RT8097B provides over current protection by
detecting low side MOSFET valley inductor current. If
the sensed valley inductor current is over the current
limit threshold (3.1A typ.), the OCP will be triggered.
When OCP is tripped, the RT8097B will keep the over
current threshold level then cause the UV protection.
Thermal Shutdown (OTP)
The device implements an internal thermal shutdown
function when the junction temperature exceeds 150C.
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 20C, the device
reinstates the power up sequence.
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8097B-06
March 2017
RT8097B
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage --------------------------------------------------------------------------------------------
0.3V
to 6.5V
LX Pin Switch Voltage-------------------------------------------------------------------------------------------
0.3V
to (V
IN
+ 0.3V)
<20ns ----------------------------------------------------------------------------------------------------------------
4.5V
to 7.5V
Power Dissipation, P
D
@ T
A
= 25C
SOT-23-5 -----------------------------------------------------------------------------------------------------------
0.45W
SOT-23-6 -----------------------------------------------------------------------------------------------------------
0.48W
Package Thermal Resistance
(Note 2)
SOT-23-5,
JA
-----------------------------------------------------------------------------------------------------
218.1C/W
SOT-23-6,
JA
-----------------------------------------------------------------------------------------------------
208.2C/W
SOT-23-5,
JC
-----------------------------------------------------------------------------------------------------
28.5C/W
SOT-23-6,
JC
-----------------------------------------------------------------------------------------------------
32C/W
Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------
260C
Junction Temperature -------------------------------------------------------------------------------------------
40C
to 150C
Storage Temperature Range ----------------------------------------------------------------------------------
65C
to 150C
ESD Susceptibility
(Note 3)
HBM (Human Body Model) ------------------------------------------------------------------------------------
2kV
Recommended Operating Conditions
(Note 4)
Supply Input Voltage --------------------------------------------------------------------------------------------
2.7V
to 6V
Ambient Temperature Range----------------------------------------------------------------------------------
40C
to 85C
Junction Temperature Range ---------------------------------------------------------------------------------
40C
to 125C
Electrical Characteristics
(V
IN
= 3.6V, T
A
= 25C, unless otherwise specified)
Parameter
Input Voltage
Feedback Reference Voltage
Feedback Leakage Current
DC Bias Current
Switching Leakage Current
Switching Frequency
Switch On Resistance, Low
Switch On Resistance, High
Valley Current Limit
Under-Voltage Lockout
Threshold
Symbol
V
IN
V
REF
I
FB
Test Conditions
Min
2.7
0.591
Typ
--
0.6
--
300
--
--
1
70
100
3.1
2.25
2
Max
6
0.609
1
--
1
1
1.2
--
--
3.9
2.5
--
Unit
V
V
A
A
A
MHz
m
m
A
V
V
V
FB
= 3.3V
Active ,V
FB
= 0.63V, not switching
Shutdown
--
--
--
--
0.8
R
NMOS
R
PMOS
I
LIM
V
UVLO
I
SW
= 0.3A
I
SW
= 0.3A
--
--
2.2
VDD rising
VDD falling
--
--
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8097B-06
March 2017
www.richtek.com
5
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