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RT8295B
2A, 23V, 1.2MHz Synchronous Step-Down Converter
General Description
The RT8295B is a high-efficiency, monolithic synchronous
step-down DC/DC converter that can deliver up to 2A
output current from a 4.5V to 23V input supply. The
RT8295B'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. The RT8295B also provides 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 RT8295B is available in a
SOP-8 (Exposed Pad) package.
Features
±
1.5% High Accuracy Feedback Voltage
4.5V to 23V Input Voltage Range
2A 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
RT8295B
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
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.
SS
EN
COMP
FB
½
Suitable for use in SnPb or Pb-free soldering processes.
GND
9
7
6
5
SOP-8 (Exposed Pad)
Marking Information
RT8295BxGSP
RT8295BxGSP : Product Number
RT8295BxZSP
RT8295BxZSP : Product Number
x : H or L
YMDNN : Date Code
RT8295Bx
GSPYMDNN
RT8295Bx
ZSPYMDNN
x : H or L
YMDNN : Date Code
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8295B-05 March 2018
www.richtek.com
1
RT8295B
Typical Application Circuit
V
IN
4.5V to 23V
2
C
IN
10µF
R
EN
100k
VIN
BOOT
RT8295B
SW 3
7 EN
8 SS
GND
1
C
BOOT
L
100nF 3.6µH
R1
75k
FB 5
COMP
6
C
C
R
C
0.82nF 32k
R2
24k
V
OUT
3.3V/2A
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 (kΩ) R2 (kΩ) R
C
(kΩ) C
C
(nF) L (μH)
8
27
3
75
0.82
10
5
62
11.8
47
0.82
6.8
3.3
75
24
32
0.82
3.6
2.5
25.5
12
25.5
0.82
3.6
1.5
10.5
12
15
0.82
2
1.2
12
24
12
0.82
2
1
3
12
10
0.82
2
C
OUT
(μF)
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 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 0.1μF 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 RT8295B into shutdown
mode reducing the supply current to less than 3μA. Attach this pin to VIN with
a 100kΩ 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 0.1μF capacitor sets the
soft-start period to 13.5ms.
FB
6
COMP
7
EN
8
SS
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8295B-05 March 2018
RT8295B
Function Block Diagram
VIN
Internal
Regulator
Shutdown
Comparator VA V
CC
1.2V
+
-
Oscillator
Foldback
Control
0.4V
+
-
UV
Comparator
Current Sense
Amplifier
Slope Comp
+
-
VA
BOOT
S
+
R
-
Current
Comparator
Q
Q
130mΩ
5k
EN
3V
Lockout
Comparator
-
+
2.7V
V
CC
6µA
SW
130mΩ
GND
SS
0.8V
+
+EA
-
FB
COMP
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8295B-05 March 2018
www.richtek.com
3
RT8295B
Absolute Maximum Ratings
(Note 1)
−0.3V
to 25V
−0.3V
to (V
IN
+ 0.3V)
−0.3V
to 6V
−0.3V
to 6V
Supply Voltage, V
IN
-------------------------------------------------------------------------------------------------
Input Voltage, SW ---------------------------------------------------------------------------------------------------
V
BOOT
−
V
SW
----------------------------------------------------------------------------------------------------------
Other Pin Voltages -------------------------------------------------------------------------------------------------
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
---------------------------------------------------------------------------------------
Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------
Junction Temperature -----------------------------------------------------------------------------------------------
Storage Temperature Range --------------------------------------------------------------------------------------
15°C/W
260°C
150°C
−65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------ 200V
(Note 4)
Recommended Operating Conditions
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
Maximum Duty Cycle
Minimum On Time
Symbol
V
EN
= 0V
Test Conditions
Min
--
--
0.788
--
--
--
Typ
0.5
0.8
0.8
940
130
130
0
4.3
4
1.2
270
75
100
Max
3
1.2
0.812
--
--
--
10
--
--
1.4
--
--
--
Unit
μA
mA
V
μA/V
mΩ
mΩ
μA
A
A/V
MHz
kHz
%
ns
V
EN
= 3 V, 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
D
MAX
t
ON
V
FB
= 0V
V
FB
= 0.7V
4.5V
≤
V
IN
≤
23V
ΔI
C
= ± 10μA
--
--
--
1
--
--
--
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8295B-05 March 2018
RT8295B
Parameter
EN Input Threshold
Voltage
Logic-High
Logic-Low
Symbol
V
IH
V
IL
V
UVLO
ΔV
UVLO
I
SS
t
SS
T
SD
V
SS
= 0V
C
SS
= 0.1μF
V
IN
Rising
Test Conditions
Min
2.7
--
3.8
--
--
--
--
Typ
--
--
4.2
320
6
13.5
150
Max
5.5
0.4
4.5
--
--
--
--
Unit
V
V
mV
μA
ms
°C
Input Under Voltage Lockout Threshold
Input Under Voltage Lockout Hysteresis
Soft-Start Current
Soft-Start Period
Thermal Shutdown
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.
θ
JA
is measured in natural convection at T
A
= 25°C on a high effective thermal conductivity four-layer test board of
JEDEC 51-7 thermal measurement standard. The measurement case position of
θ
JC
is on 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.
DS8295B-05 March 2018
www.richtek.com
5
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