®
RT8296B
3A, 23V, 1.2MHz Synchronous Step-Down Converter
General Description
The RT8296B is a high-efficiency, monolithic synchronous
step-down DC/DC converter that can deliver up to 3A
output current from a 4.5V to 23V input supply. The
RT8296B's current mode architecture and external
compensation allow the transient response to be
optimized over a wide range of loads and output capacitors.
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 and thermal shutdown protection.
The low current (<3μA) shutdown mode provides output
disconnection, enabling easy power management in
battery-powered systems. The RT8296B is available in
an SOP-8 (Exposed Pad) package.
Features
±
1.5% High Accuracy Feedback Voltage
4.5V to 23V Input Voltage Range
3A Output Current
Integrated N-MOSFET Switches
Current Mode Control
Fixed Frequency Operation : 1.2MHz
Adjustable Output from 0.8V to 15V
Up to 95% Efficiency
Programmable Soft-Start
Stable with Low-ESR Ceramic Output Capacitors
Cycle-by-Cycle Over Current Protection
Input Under Voltage Lockout
Output Under Voltage Protection
Thermal Shutdown Protection
RoHS Compliant and Halogen Free
Ordering Information
RT8296B
Package Type
SP : SOP-8 (Exposed Pad-Option 1)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
H : UVP Hiccup
L : UVP Latch-Off
Note :
Richtek products are :
½
Applications
External Storage Device
Wireless AP/Router
Set-Top-Box
Industrial and Commercial Low Power Systems
LCD Monitors and TVs
Green Electronics/Appliances
Point of Load Regulation of High-Performance DSPs
Pin Configurations
(TOP VIEW)
BOOT
VIN
SW
GND
2
3
4
8
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.
SS
EN
COMP
FB
½
GND
9
7
6
5
Marking Information
RT8296BxGSP
RT8296BxGSP : Product Number
SOP-8 (Exposed Pad)
RT8296Bx
GSPYMDNN
RT8296BxZSP
x : H or L
YMDNN : Date Code
RT8296BxZSP : Product Number
RT8296Bx
ZSPYMDNN
x : H or L
YMDNN : Date Code
is a registered trademark of Richtek Technology Corporation.
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
DS8296B-05 July 2014
www.richtek.com
1
RT8296B
Typical Application Circuit
V
IN
4.5V to 23V
2
C
IN
10µF x 2
R
EN
100k
VIN
BOOT
RT8296B
SW 3
7 EN
8 SS
GND
1
C
BOOT
L
100nF 3.6µH
R1
75k
FB 5
COMP
6
C
C
2.2nF
R
C
22k
R2
24k
V
OUT
3.3V/3A
C
OUT
22µF x 2
C
SS
0.1µF
4, 9 (Exposed Pad)
C
P
Open
Table 1. Recommended Component Selection
V
OUT
(V) R1 (k) R2 (k) R
C
(k) C
C
(nF) L (H)
C
OUT
(F)
8
27
3
51
2.2
10
22 x 2
5
62
11.8
33
2.2
6.8
22 x 2
3.3
75
24
22
2.2
3.6
22 x 2
2.5
25.5
12
16
2.2
3.6
22 x 2
1.5
10.5
12
10
2.2
2
22 x 2
1.2
12
24
8.2
2.2
2
22 x 2
1
3
12
6.8
2.2
2
22 x 2
Functional Pin Description
Pin No.
1
2
3
4,
9 (Exposed Pad)
5
Pin Name
BOOT
VIN
SW
GND
Pin Function
Bootstrap for High Side Gate Driver. Connect a 0.1F or greater ceramic
capacitor from BOOT to SW pins.
Input Supply Voltage, 4.5V to 23V. Must bypass with a suitably large ceramic
capacitor.
Switch Node. Connect this pin to an external L-C filter.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Feedback Input. This pin is connected to the converter output. It is used to set
the output of the converter to regulate to the desired value via an internal
resistive voltage divider. For an adjustable output, an external resistive
voltage divider is connected to this pin.
Compensation Node. COMP is used to compensate the regulation control
loop. Connect a series RC network from COMP to GND. In some cases, an
additional capacitor from COMP to GND is required.
Chip Enable (Active High). A logic-low forces the RT8296B into shutdown
mode reducing the supply current to less than 3A. Attach this pin to VIN with
a 100k pull up resistor for automatic startup.
Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor
from SS to GND to set the soft-start period. A 0.1F capacitor sets the
soft-start period to 13.5ms.
FB
6
COMP
7
EN
8
SS
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8296B-05 July 2014
RT8296B
Function Block Diagram
VIN
Internal
Regulator
Shutdown
Comparator V
A
V
CC
1.2V
+
-
Lockout
Comparator
-
2.7V
3V
+
0.4V
Oscillator
Foldback
Control
+
Current Sense
Amplifier
Slope Comp
+
-
V
A
BOOT
S
+
R
-
Current
Comparator
Q
Q
85m
SW
85m
5k
EN
-
UV
Comparator
GND
V
CC
6µA
SS
0.8V
+
+EA
-
FB
COMP
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8296B-05 July 2014
www.richtek.com
3
RT8296B
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage, V
IN
------------------------------------------------------------------------------------------
−
0.3V to 25V
Switch Node Voltage, V
SW
----------------------------------------------------------------------------------------
−0.3V
to (V
IN
+ 0.3V)
Switch Node Voltage, V
SW
, < 10ns -----------------------------------------------------------------------------
−5V
to 25.3V
BOOT Pin Voltage, V
BOOT
----------------------------------------------------------------------------------------
−0.3V
to 31.3V
V
BOOT
- V
SW
-----------------------------------------------------------------------------------------------------------
−0.3V
to 6V
Other Pin Input Voltages ------------------------------------------------------------------------------------------
−0.3V
to 6V
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------- 1.333W
Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad),
θ
JA
---------------------------------------------------------------------------------------- 75°C/W
SOP-8
(Εxposed
Pad),
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 Voltage, V
IN
------------------------------------------------------------------------------------------------- 4.5V to 23V
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 Supply Current
Supply Current
Feedback Voltage
Error Amplifier
Transconductance
High Side Switch
On-Resistance
Low Side Switch
On-Resistance
High Side Switch Leakage
Current
Upper Switch Current Limit
COMP to Current Sense
Transconductance
Oscillation Frequency
Short Circuit Oscillation
Frequency
Symbol
V
EN
= 0V
Test Conditions
Min
--
--
0.788
--
--
--
Typ
0.5
0.8
0.8
940
85
85
0
5.1
5.4
1.2
270
Max
3
1.2
0.812
--
--
--
10
6.6
--
1.4
--
Unit
A
mA
V
A/V
m
m
A
A
A/V
MHz
kHz
V
EN
= 3V, V
FB
= 0.9V
V
FB
G
EA
R
DS(ON)1
R
DS(ON)2
V
EN
= 0V, V
SW
= 0V
Min. Duty Cycle, V
BOOT
V
SW
= 4.8V
G
CS
f
OSC1
f
OSC2
V
FB
= 0V
4.5V
V
IN
23V
I
C
= ±10A
--
3.6
--
1
--
Copyright
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8296B-05 July 2014
RT8296B
Parameter
Maximum Duty Cycle
Minimum On-Time
EN Input Voltage
Logic-High
Symbol
D
MAX
t
ON
V
IH
V
IL
V
UVLO
V
UVLO
I
SS
t
SS
T
SD
V
SS
= 0V
C
SS
= 0.1F
V
IN
Rising
Test Conditions
V
FB
= 0.7V
Min
--
--
2.7
--
3.8
--
--
--
--
Typ
75
100
--
--
4.2
320
6
13.5
150
Max
--
--
5.5
0.4
4.5
--
--
--
--
Unit
%
ns
V
V
mV
A
ms
C
Logic-Low
Input Under Voltage Lockout
Threshold
Input Under Voltage Lockout
Hysteresis
Soft-Start Current
Soft-Start Period
Thermal Shutdown
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
©
2014 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8296B-05 July 2014
www.richtek.com
5
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