RT7296E
3A, 17V Current Mode Synchronous Step-Down Converter
General Description
The RT7296E is a high-efficiency, 3A current mode
synchronous step-down DC/DC converter with a wide
input voltage range from 6V to 17V. The device
integrates 80m
high-side
and
30m
low-side
Features
6V to 17V Input Voltage Range
3A Output Current
Internal N-Channel MOSFETs
Current Mode Control
Fixed Switching Frequency : 800kHz
Cycle-by-Cycle Current Limit
TTH Power-Save Mode
External Soft-Start Function
Input Under-Voltage Lockout
Output Under-Voltage Protection
Thermal Shutdown
MOSFETs to achieve high efficiency conversion. The
current
mode control
architecture supports fast
transient response and internal compensation. A
cycle-by-cycle current limit function provides protection
against
complete
shorted output.
protection
The RT7296E
such
provides
as
input
functions
under-voltage lockout, output under-voltage protection,
over-current protection, and thermal shutdown. The
RT7296E is available in the TSOT-23-8 (FC) package.
Applications
Industrial and Commercial Low Power Systems
Computer Peripherals
LCD Monitors and TVs
Set-top Boxes
Ordering Information
RT7296E
Package Type
J8F : TSOT-23-8 (FC)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
RoHS compliant and compatible with the current
requirements of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
09=DNN
09= : Product Code
DNN : Date Code
Simplified Application Circuit
RT7296E
BOOT
VIN
C1
SW
PVCC
C2
R3
TTH
R4
GND
SS
C5
R5
FB
R2
C4
R1
C3
L1
V
OUT
V
IN
Copyright © 2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7296E-02
May 2016
www.richtek.com
1
RT7296E
Pin Configurations
(TOP VIEW)
BOOT
5
4
PVCC
7
2
8
SW
SS
6
3
FB
TSOT-23-8 (FC)
Functional Pin Description
Pin No.
1
2
3
4
5
6
7
8
Pin Name
TTH
VIN
SW
GND
BOOT
SS
PVCC
FB
Pin Function
Transition Threshold. Connect a resistor divider to let the RT7296E into power
saving mode under light loads. Connect to PVCC to force RT7296E into CCM.
Power Input. Support 6V to17V Input Voltage. Must bypass with a suitable
large ceramic capacitor at this pin.
Switch Node. Connect to external L-C filter.
System Ground.
Bootstrap Supply for High-Side Gate Driver. Connect a 0.1F ceramic
capacitor between the BOOT and SW pins.
Soft-Start Control Input. SS control the soft-start period. Connect a capacitor
from SS to GND to set the soft-start period.
5V Bias Supply Output. Connect a minimum of 0.1F capacitor to ground.
Feedback Voltage Input. The pin is used to set the output voltage of the
converter to regulate to the desired voltage via a resistive divider. Feedback
reference = 0.8V.
Copyright © 2016 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
GND
is a registered trademark of Richtek Technology Corporation.
TTH
VIN
DS7296E-02
May 2016
RT7296E
Function Block Diagram
TTH
PVCC
VIN
Internal
Regulator
UVLO
BOOT
UVLO
Current
Sense
BOOT
Logic &
Protection
Control
0.4V
+
-
UV
Comparator
1pF
50pF
FB
0.807V
10.5µA
400k
-
+ EA
+
Oscillator
HS Switch
Current
Comparator
Slope
Compensation
LS Switch
Current
Comparator
Current
Sense
GND
Power
Stage &
Deadtime
Control
SW
SS
Operation
Under Voltage Lockout Threshold
The IC includes an input Under Voltage Lockout
Protection (UVLO). If the input voltage exceeds the
UVLO rising threshold voltage (3.9V), the converter
resets and prepares
the PWM for operation. If the input voltage falls below
the UVLO falling threshold voltage (3.25V) during
normal operation, the device stops switching. The
UVLO rising and falling threshold voltage includes a
hysteresis to prevent noise caused reset.
Internal Regulator
The internal regulator generates 5V power and drive
internal circuit. When VIN is below 5V, PVCC will drop
with VIN. A capacitor(>0.1F) between PVCC and
GND is required.
Soft-Start Function
The RT7296E provides external soft-start function. The
soft-start function is used to prevent large inrush
current while converter is being powered-up. The
soft-start timing can be programmed by the external
capacitor between SS pin and GND. The Chip provides
a 11A charge current for the external capacitor.
Copyright © 2016 Richtek Technology Corporation. All rights reserved.
Over Current Protection
RT7296E provides cycle-by-cycle over current limit
protection. When the inductor current peak value
reaches current limit, IC will turn off High Side MOS to
avoid over current.
Under Voltage Protection (Hiccup Mode)
RT7296E provides Hiccup Mode of Under Voltage
Protection (UVP). When the FB voltage drops below
half of the feedback reference voltage, V
FB
, the UVP
function will be triggered and the IC will shut down for a
period of time and then recover automatically. The
Hiccup Mode of UVP can reduce input current in
short-circuit conditions.
Thermal Shutdown
Thermal shutdown is implemented to prevent the chip
from operating at excessively high temperatures. When
the junction temperature is higher than 150
o
C, the chip
will shutdown the switching operation. The chip is
automatically re-enabled when the junction temperature
cools down by approximately 20
o
C.
is a registered trademark of Richtek Technology Corporation.
DS7296E-02
May 2016
www.richtek.com
3
RT7296E
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage, VIN
-----------------------------------------------------------------------------------
0.3V
to 20V
Switch Voltage, SW
--------------------------------------------------------------------------------------------
0.3V
to V
IN
+ 0.3V
<20ns
---------------------------------------------------------------------------------------------------------------
5V
BOOT to SW, V
BOOT – SW
-----------------------------------------------------------------------------------
0.3V
to 6V (7V for < 10s)
Bias Supply Output, PVCC----------------------------------------------------------------------------------
0.3V
to 6V (7V for < 10s)
Other Pins---------------------------------------------------------------------------------------------------------
0.3V
to 6V
Power Dissipation, P
D
@ T
A
= 25C
TSOT-23-8 (FC)
------------------------------------------------------------------------------------------------
1.428W
Package Thermal Resistance
(Note 2)
TSOT-23-8 (FC),
JA
-----------------------------------------------------------------------------------------
70C/W
TSOT-23-8 (FC),
JC
-----------------------------------------------------------------------------------------
15C/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, VIN ------------------------------------------------------------------------------6V to 17V
Junction Temperature Range
------------------------------------------------------------------------------
40C
to 125C
Ambient Temperature Range
------------------------------------------------------------------------------
40C
to 85C
Electrical Characteristics
(V
IN
= 12V, T
A
= 25C, unless otherwise specified)
Parameter
Quiescent Current with no Load
at DCDC Output
Feedback Voltage
Feedback Current
Switch
On-Resistance
Current Limit
Low-Side Switch Current Limit
Oscillation Frequency
Fold-Back Frequency
Maximum Duty-Cycle
Minimum On-Time
Input Under-Voltage
Lockout Threshold
V
IN
Rising
High-Side
Low-Side
Symbol
Test Conditions
V
EN
= 2V, V
FB
= 1V, TTH = 0.5V
Min
--
0.799
Typ
0.8
0.807
10
80
30
5
2
800
125
92
60
5.3
1.1
Max
1
0.815
50
--
--
--
--
--
--
--
--
5.85
--
Unit
mA
V
nA
m
A
A
kHz
kHz
%
ns
V
V
V
FB
I
FB
R
DS(ON)H
R
DS(ON)L
I
LIM
Under 40% duty-cycle
From Drain to Source
f
OSC
V
FB
= 0.75V
V
FB
< 400mV
D
MAX
t
ON
V
UVLO
V
IN
Rising
Hysteresis
V
UVLO
V
FB
= 0.7V
V
FB
= 820mV
--
--
--
4.2
--
--
--
87
--
4.9
--
Copyright © 2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS7296E-02
May 2016
RT7296E
Parameter
PVCC Regulator
PVCC Load Regulation
Soft-Start Charge Current
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
Symbol
V
CC
V
LOAD
I
SS
T
SD
T
SD
I
VCC
= 5mA
Test Conditions
Min
--
--
7.6
--
--
Typ
5
3
10.5
150
20
Max
--
--
13.4
--
--
Unit
V
%
A
o
o
C
C
Note 1.
Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2.
JA
is measured at T
A
= 25C on a high effective thermal conductivity four-layer test board per JEDEC 51-7.
JC
is
measured at the exposed pad of the package.
Note 3.
Devices are ESD sensitive. Handling precaution recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
Copyright © 2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7296E-02
May 2016
www.richtek.com
5
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