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RT8294
2A, 23V, 340kHz Synchronous Step-Down Converter
General Description
The RT8294 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 RT8294'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 RT8294 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
RT8294 is available in SOP-8 and SOP-8 (Exposed Pad)
packages.
Features
±
1.5% High Accuracy Feedback Voltage
Input Voltage Range : 4.5V to 23V
2A Output Current
Integrated N-MOSFETs
Current Mode Control
340kHz Fixed Frequency Operation
Output Adjustable Voltage Range : 0.923V to 20V
Efficiency Up to 95%
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
RT8294
Package Type
S : SOP-8
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)
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
7
6
5
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.
½
SS
EN
COMP
FB
SOP-8
BOOT
VIN
SW
GND
2
3
4
8
SS
EN
COMP
FB
GND
9
7
6
5
SOP-8 (Exposed Pad)
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8294-03
October 2016
www.richtek.com
1
RT8294
Marking Information
RT8294GS
RT8294GS : Product Number
RT8294GSP
RT8294GSP : Product Number
YMDNN : Date Code
RT8294
GSYMDNN
RT8294
GSPYMDNN
YMDNN : Date Code
RT8294ZSP
RT8294ZSP : Product Number
RT8294
ZSPYMDNN
YMDNN : Date Code
Typical Application Circuit
V
IN
4.5V to 23V
2
C
IN
10µF
R
EN
100k
VIN
BOOT
RT8294
7 EN
8 SS
GND
1
C
BOOT
L
10nF 10µH
R1
26.1k
FB 5
COMP
6
C
C
3.3nF
R
C
13k
R2
10k
V
OUT
3.3V/2A
C
OUT
22µF x 2
SW 3
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)
8
76.8
10
27
3.3
22
5
45.3
10
20
3.3
15
3.3
26.1
10
13
3.3
10
2.5
16.9
10
9.1
3.3
6.8
1.8
9.53
10
5.6
3.3
4.7
1.2
3
10
3.6
3.3
3.6
C
OUT
(F)
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8294-03
October 2016
RT8294
Functional Pin Description
Pin No.
SOP-8
1
2
3
4
SOP-8
(Exposed Pad)
1
2
Pin Name
Pin Function
Bootstrap for High Side Gate Driver. Connect a 10nF or greater
ceramic capacitor from BOOT to SW pins.
Input Supply Voltage, 4.5V to 23V. Must bypass with a suitably large
ceramic capacitor.
Phase Node. Connect this pin to 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 Pin. 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.
Enable Input pin. A logic high enables the converter; a logic low
forces the RT8294 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 15.5ms .
BOOT
VIN
3
SW
4,
GND
9 (Exposed Pad)
5
FB
5
6
6
COMP
7
7
EN
8
8
SS
Function Block Diagram
VIN
Internal
Regulator
Shutdown
Comparator VA V
CC
1.2V
+
-
Oscillator
Foldback
Control
0.5V
+
Current Sense
Amplifier
Slope Comp
+
-
VA
EN
5k
Lockout
Comparator
-
+
2.7V
V
CC
6µA
-
UV
Comparator
BOOT
S
+
R
-
Current
Comparator
Q
Q
130m
SW
130m
3V
GND
SS
0.923V
+
+
-
Error Amp
COMP
is a registered trademark of Richtek Technology Corporation.
FB
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
DS8294-03
October 2016
www.richtek.com
3
RT8294
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 Pins Voltages -----------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 ------------------------------------------------------------------------------------------------------------------ 1.111W
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------- 1.333W
Package Thermal Resistance (Note 2)
SOP-8,
θ
JA
------------------------------------------------------------------------------------------------------------
SOP-8 (Exposed Pad),
θ
JA
----------------------------------------------------------------------------------------
SOP-8 (Exposed Pad),
θ
JC
---------------------------------------------------------------------------------------
Junction Temperature ----------------------------------------------------------------------------------------------
90°C/W
75°C/W
15°C/W
150°C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°C
Storage Temperature Range -------------------------------------------------------------------------------------
−65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) --------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ----------------------------------------------------------------------------------------------- 200V
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
High-Side Switch-On Resistance
Low-Side Switch-On Resistance
High-Side Switch Leakage Current
Upper Switch Current Limit
Low Switch Current Limit
COMP to Current Sense
Transconductance
Oscillator Frequency
Short Circuit Oscillation
Frequency
Maximum Duty Cycle
Minimum On-Time
Symbol
I
CC
V
FB
R
DS(ON)1
R
DS(ON)2
Test Conditions
V
EN
= 0V
V
EN
= 3 V, V
FB
= 1V
4.5V
≦
V
IN
≦
23V
∆I
C
= ± 10A
Min
--
--
0.909
--
--
--
Typ
0.5
0.8
0.923
940
130
130
0
4.3
1.3
4
340
100
93
100
Max
3
1.2
0.937
--
--
--
10
--
--
--
380
--
--
--
Unit
A
mA
V
A/V
m
m
A
A
A
A/V
kHz
kHz
%
ns
Error Amplifier Transconductance G
EA
V
EN
= 0V, V
SW
= 0V
Min.Duty Cycle, V
BOOTSW
= 4.8V
From Drain to Source
G
CS
f
OSC1
f
OSC2
V
FB
= 0V
V
FB
= 0.7V
--
--
--
--
300
--
--
--
D
MAX
t
ON
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8294-03
October 2016
RT8294
Parameter
EN Input Threshold
Voltage
Logic High
Logic Low
Symbol
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
Min
2.7
--
3.8
--
--
--
--
Typ
--
--
4.2
320
6
15.5
150
Max
5.5
0.4
4.5
--
--
--
--
Unit
V
V
mV
A
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
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8294-03
October 2016
www.richtek.com
5
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