®
RT8297A/B
1.5A, 17V, 340/800kHz Synchronous Step-Down Converter
General Description
The RT8297A/B is a high efficiency, monolithic
synchronous step-down DC/DC converter that can operate
at 340kHz/800kHz, while delivering up to 1.5A output
current from a 4V to 17V input supply. The RT8297A/B's
current mode architecture allows the transient response
to be optimized. Cycle-by-cycle current limit provides
protection against shorted outputs and soft-start eliminates
input current surge during start-up. Fault conditions also
include output under voltage protection, output over voltage
protection, and thermal shutdown. The low current (<5μA)
shutdown mode provides output disconnect, enabling easy
power management in battery-powered systems. The
RT8297A/B is available in a WDFN-8L 2x2 package.
Features
4V to 17V Input Voltage Range
1.5A Output Current
Internal N-MOSFETs
Current Mode Control
Fixed Frequency Operation : 340kHz/800kHz
Output Adjustable from 0.8V to 12V
Up to 95% Efficiency
Internal Compensation
Stable with Low ESR Ceramic Output Capacitors
Cycle-by-Cycle Over Current Protection
Input Under Voltage Lockout
Output Under Voltage Protection
Output Over Voltage Protection
Power Good Indicator
Thermal Shutdown Protection
RoHS Compliant and Halogen Free
Ordering Information
RT8297A/B
Package Type
QW : WDFN-8L 2x2 (W-Type)
Lead Plating System
Z : ECO (Ecological Element with
Halogen Free and Pb free)
A : 340kHz
B : 800kHz
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
BOOT
EN
1
2
3
4
8
7
6
5
Marking Information
RT8297AZQW
00 : Product Code
W : Date Code
9
GND
GND
PGOOD
FB
WDFN-8L 2x2
00W
RT8297BZQW
71 : Product Code
71W
W : Date Code
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8297A/B-06 June 2013
GND
www.richtek.com
1
RT8297A/B
Typical Application Circuit
RT8297A
V
IN
4V to 17V
2 VIN
C
IN
10µF
6 PGOOD
4 EN
GND
SW 1
FB 5
R2
36k
BOOT 3
C
BOOT
10nF
L
15µH
V
OUT
3.3V
1.5A
C
OUT
22µF x 2
PGOOD
Chip Enable
R1
110k
7, 8, 9 (Exposed Pad)
RT8297B
V
IN
4V to 17V
2 VIN
C
IN
10µF
6 PGOOD
4 EN
GND
SW 1
FB 5
R2
15k
BOOT 3
C
BOOT
10nF
L
6.8µH
R1
47k
V
OUT
3.3V
1.5A
C
OUT
22µF x 2
PGOOD
Chip Enable
7, 8, 9 (Exposed Pad)
Table 1. Recommended Component Selection
RT8297A
V
OUT
(V)
1.2
2.5
3.3
5
L (μH)
4.7
10
15
22
R1 (kΩ)
110
110
110
120
R2 (kΩ)
220
51
36
22
C
OUT
(μF)
22 x 2
22 x 2
22 x 2
22 x 2
RT8297B
V
OUT
(V)
1.2
2.5
3.3
5
L (μH)
3.6
4.7
6.8
10
R1 (kΩ)
47
47
47
62
R2 (kΩ)
91
22
15
12
C
OUT
(μF)
22 x 2
22 x 2
22 x 2
22 x 2
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8297A/B-06 June 2013
RT8297A/B
Functional Pin Description
Pin No.
1
2
3
Pin Name
SW
VIN
BOOT
Pin Function
Switch Node. Connect to external L-C filter.
Input Supply Voltage. Must bypass with a suitably large ceramic
capacitor.
Bootstrap for High Side Gate Driver. Connect 0.01μF or greater ceramic
capacitor from BOOT to SW pin.
Chip Enable. A logic-high enables the converter; a logic-low forces the
RT8297A/B into shutdown mode, reducing the supply current to less
than 5μA. Attach this pin to VIN with a 100kΩ pull up resistor for
automatic startup.
Feedback Input Pin. For an adjustable output, connect an external
resistive voltage divider to this pin.
Power Good Indicator. The output of this pin is low if the output voltage is
12.5% less than the nominal voltage. Otherwise, it is an open drain.
Ground. The exposed pad must be soldered to a large PCB and
connected to GND for maximum power dissipation.
4
EN
5
6
7, 8, 9 (Exposed Pad)
FB
PGOOD
GND
Function Block Diagram
VIN
Internal
Regulator
Enable
Comparator
+
2.5V
-
5k
3V
1V
+
OSC
340kHz/800kHz
Slope Comp
+
V
A
V
CC
Foldback
Control
EN
Current Sense
Amplifier
-
V
A
OV
-
OV Comparator
+
-
+
BOOT
S
-
Q
Q
145m
0.4V
UV
R
Current
Comparator
SW
140m
UV Comparator
0.8V
FB
+
-
Error Amp
35pF 400k
1pF
PGOOD
Comparator
+
-
GND
0.7V
FB
PGOOD
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8297A/B-06 June 2013
www.richtek.com
3
RT8297A/B
Absolute Maximum Ratings
(Note 1)
Supply Voltage, VIN -----------------------------------------------------------------------------------------
−0.3V
to 19V
SW ---------------------------------------------------------------------------------------------------------------
−0.3V
to (V
IN
+ 0.3V)
BOOT to SW --------------------------------------------------------------------------------------------------
−0.3V
to 6V
All Other Pins -------------------------------------------------------------------------------------------------
−0.3V
to 6V
Power Dissipation, P
D
@ T
A
= 25°C
WDFN-8L 2x2 ------------------------------------------------------------------------------------------------- 0.833W
Package Thermal Resistance (Note 2)
WDFN-8L 2x2,
θ
JA
-------------------------------------------------------------------------------------------- 120°C/W
WDFN-8L 2x2,
θ
JC
-------------------------------------------------------------------------------------------- 8.2°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
MM (Machine Model) ---------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
(Note 4)
Supply Input Voltage, VIN ---------------------------------------------------------------------------------- 4V to 17V
Junction Temperature Range -------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
Parameter
Shutdown Supply Current
Supply Current
Feedback Current
High Side Switch On
Resistance
Low Side Switch On
Resistance
Upper Switch Current Limit
Lower Switch Current Limit
Oscillation Frequency
Short-Circuit Oscillation
Frequency
Maximum Duty Cycle
f
OSC1
f
OSC2
D
MAX
I
SHDN
I
OUT
I
FB
(V
IN
= 12V, T
A
= 25°C, unless otherwise specified)
Symbol
V
EN
= 0V
Test Conditions
V
EN
= 3V, V
FB
= 0.9V
4V
≤
V
IN
≤
17V
V
FB
= 0.8V
Min
--
--
0.788
--
--
--
Typ
1
0.6
0.800
10
145
140
3
1
340
800
95
170
93
84
Max
5
1
0.812
--
--
--
4.65
--
380
900
--
--
--
--
Unit
μA
mA
V
nA
mΩ
mΩ
A
A
kHz
kHz
%
%
Feedback Reference Voltage V
REF
R
DS(ON)1
R
DS(ON)2
Min. Duty Cycle, V
BOOT
−
V
SW
= 4.8V
Maximum Loading = 1.5A
From Drain to Source
For RT8297A
For RT8297B
V
FB
= 0V, For RT8297A
V
FB
= 0V, For RT8297B
V
FB
= 0.7V, For RT8297A
V
FB
= 0.7V, For RT8297B
2.45
--
300
700
--
--
--
--
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8297A/B-06 June 2013
RT8297A/B
Parameter
Minimum On-Time
Input Under Voltage Lockout
Threshold
Input Under Voltage Lockout
Threshold Hysteresis
EN Threshold
Voltage
Symbol
t
ON
V
UVLO
ΔV
UVLO
Test Conditions
Min
--
--
--
2.5
--
V
EN
= 2V, V
FB
= 1V
t
SS
T
SD
ΔT
SD
--
--
--
--
--
--
--
--
--
--
--
Typ
100
3.5
200
--
--
1
1
150
15
0.7
130
12
125
10
50
2
Max
125
--
--
--
0.4
--
--
--
--
--
--
--
--
--
--
--
Unit
ns
V
mV
V
μA
ms
°C
°C
V
mV
Ω
%V
REF
μs
%V
REF
μs
Logic-High V
IH
Logic-Low
VIL
EN Pull Low Current
Soft-Start Period
Thermal Shutdown
Thermal Shutdown
Hysteresis
Power Good Threshold
Rising
Power Good Threshold
Hysteresis
Power Good Pull Down
Resistance
Output OVP Trip Threshold
Output OVP Prop Delay
Output UVP Trip Threshold
Output UVP Prop Delay
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.
Note 3.
Devices are ESD sensitive. Handling precaution is recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8297A/B-06 June 2013
www.richtek.com
5
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