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RT8290
3A, 23V, 340kHz Synchronous Step-Down Converter
General Description
The RT8290 is a high efficiency synchronous step-down
DC/DC converter that can deliver up to 3A output current
from 4.5V to 23V input supply. The RT8290'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 RT8290 also
provides 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 RT8290
is awailable in an SOP-8 (Exposed Pad) package.
Features
4.5V to 23V Input Voltage Range
1.5% High Accuracy Feedback Voltage
3A Output Current
Integrated N-MOSFET Switches
Current Mode Control
Fixed Frequency Operation : 340kHz
Output Adjustable from 0.925V to 20V
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
Thermally Enhanced SOP-8 (Exposed Pad) Package
RoHS Compliant and Halogen Free
Applications
Industrial and Commercial Low Power Systems
Computer Peripherals
LCD Monitors and TVs
Green Electronics/Appliances
Point of Load Regulation of High-Performance DSPs,
FPGAs and ASICs.
Ordering Information
RT8290
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)
Note :
Richtek products are :
½
Pin Configurations
(TOP VIEW)
BOOT
VIN
SW
GND
2
3
4
8
SS
EN
COMP
FB
GND
9
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.
SOP-8 (Exposed Pad)
½
Typical Application Circuit
V
IN
4.5V to 23V
2
R
EN
100k
C
IN
10µFx2
VIN
BOOT
RT8290
7 EN
8 SS
C
SS
0.1µF
4,
9 (Exposed Pad)
1
C
BOOT
L1
10nF 10µH
R1
26.1k
FB 5
COMP
6
C
C
R
C
3.9nF 6.8k
R2
10k
V
OUT
3.3V/3A
C
OUT
22µFx2
SW 3
GND
C
P
NC
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8290-04
October 2016
www.richtek.com
1
RT8290
Marking Information
RT8290GSP : Product Number
RT8290ZSP : Product Number
RT8290
GSPYMDNN
YMDNN : Date Code
RT8290
ZSPYMDNN
YMDNN : Date Code
Table 1. Recommended Component Selection
V
OUT
(V)
R1 (k)
R2 (k)
R
C
(k)
C
C
(nF)
L (μH)
C
OUT
(μF)
15
10
8
5
3.3
2.5
1.8
1.2
153
97.6
76.8
45.3
26.1
16.9
9.53
3
10
10
10
10
10
10
10
10
30
20
15
13
6.8
6.2
4.3
3
3.9
3.9
3.9
3.9
3.9
3.9
3.9
3.9
33
22
22
15
10
6.8
4.7
3.6
22 x 2
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
6
Pin Name
BOOT
VIN
SW
GND
FB
COMP
Pin Function
Bootstrap for High Side Gate Driver. Connect a 10nF or greater ceramic capacitor
from the BOOT pin to SW pin.
Voltage Supply Input. The input voltage range is from 4.5V to 23V. A suitable large
capacitor must be bypassed with this pin.
Switching Node. Connect the output LC filter between the SW pin and output load.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Output Voltage Feedback Input. The feedback reference voltage is 0.925V
typically.
Compensation Node. This pin is used for compensating the regulation control
loop. A series RC network is required to be connected from COMP to GND. If
needed, an additional capacitor can be connected from COMP to GND.
Enable Input. A logic high enables the converter, a logic low forces the converter
into shutdown mode reducing the supply current to less than 3A. For automatic
startup, connect this pin to VIN with a 100k pull up resistor.
Soft-Start Control Input. The soft-start period can be set by connecting a capacitor
from SS to GND. A 0.1F capacitor sets the soft-start period to 15.5ms typically.
7
8
EN
SS
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8290-04
October 2016
RT8290
Function Block Diagram
VIN
Internal
Regulator
Shutdown
Comparator
+
1.2V
EN
5k
-
-
+
2.5V
Lockout
Comparator
V
CC
7µA
SS
0.925V
+
+ EA
-
0.5V
VA V
CC
Oscillator
Current Sense
Slope Comp Amplifier
+
-
Foldback
Control
+
BOOT
S
+
-
Current
Comparator
R
Q
Q
100m
SW
85m
GND
VA
3V
-
UV
Comparator
FB
COMP
Absolute Maximum Ratings
(Note 1)
−0.3V
to 25V
−0.3V
to (V
IN
+
0.3V)
−5V
to 30V
(V
SW
−
0.3V) to (V
SW
+
6V)
−0.3V
to 6V
1.333W
75°C/W
15°C/W
150°C
260°C
−65°C
to 150°C
2kV
200V
Supply Voltage, V
IN
------------------------------------------------------------------------------------------
Switching Voltage, SW -------------------------------------------------------------------------------------
SW (AC) 30ns -------------------------------------------------------------------------------------------------
BOOT Voltage -------------------------------------------------------------------------------------------------
The Other Pins ------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad),
θ
JA
---------------------------------------------------------------------------------
SOP-8 (Exposed Pad),
θ
JC
--------------------------------------------------------------------------------
Junction Temperature ----------------------------------------------------------------------------------------
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------
Storage Temperature Range -------------------------------------------------------------------------------
ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------
MM (Machine Model) ----------------------------------------------------------------------------------------
(Note 4)
Recommended Operating Conditions
Supply Voltage, V
IN
------------------------------------------------------------------------------------------
Enable Voltage, V
EN
-----------------------------------------------------------------------------------------
Junction Temperature Range -------------------------------------------------------------------------------
Ambient Temperature Range -------------------------------------------------------------------------------
4.5V to 23V
0V to 5.5V
−40°C
to 125°C
−40°C
to 85°C
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8290-04
October 2016
www.richtek.com
3
RT8290
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
Lower Switch Current Limit
COMP to Current Sense
Transconductance
Oscillation Frequency
Short Circuit Oscillation Frequency
Maximum Duty Cycle
Minimum On Time
EN Input Threshold Logic-High
Voltage
Logic-Low
Input Under Voltage Lockout
Threshold
Input Under Voltage Lockout
Threshold Hysteresis
Soft-Start Current
Soft-Start Period
Thermal Shutdown
Symbol
Test Conditions
V
EN
= 0V
V
EN
= 3V, V
FB
= 1V
Min
--
--
0.911
--
--
--
Typ
0.3
0.8
0.925
940
100
85
0
5.1
1.5
5.4
340
100
90
100
--
--
4.2
320
6
15.5
150
Max
3
1.2
0.939
--
--
--
10
--
--
--
380
--
--
--
--
0.4
4.5
--
--
--
--
Unit
A
mA
V
A/V
m
m
A
A
A
A/V
kHz
kHz
%
ns
V
V
mV
A
ms
°C
V
FB
G
EA
R
DS(ON)1
R
DS(ON)2
4.5V
V
IN
23V
I
C
= ±10A
V
EN
= 0V, V
SW
= 0V
Min. Duty Cycle
V
BOOT
V
SW
= 4.8V
From Drain to Source
G
CS
f
OSC1
f
OSC2
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
V
FB
= 0V
V
FB
= 0.8V
--
--
--
--
300
--
--
--
2.7
--
3.8
--
--
--
--
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
©
2016 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8290-04
October 2016
RT8290
Typical Operating Characteristics
Efficiency vs. Output Current
100
90
0.932
0.930
0.928
0.926
0.924
0.922
0.920
Reference Voltage vs. Input Voltage
Efficiency (%)
70
60
50
40
30
20
10
0
0
V
OUT
= 3.3V
0.5
1
1.5
2
2.5
3
Reference Voltage (V)
80
V
IN
= 4.5V
V
IN
= 12V
V
IN
= 23V
4
6
8
10
12
14
16
18
20
22
24
Output Current (A)
Input Voltage (V)
Reference Voltage vs. Temperature
0.940
0.935
Output Voltage vs. Output Current
3.320
3.318
Reference Voltage (V)
0.930
0.925
0.920
0.915
0.910
-50
-25
0
25
50
75
100
125
Output Voltage (V)
3.315
3.313
3.310
3.308
3.305
3.303
3.300
0
0.5
1
1.5
2
V
IN
= 4.5V
V
IN
= 12V
V
IN
= 23V
V
OUT
= 3.3V
2.5
3
Temperature (
C)
Output Current (A)
Frequency vs. Input Voltage
350
345
340
350
345
340
Frequency vs. Temperature
Frequency (kHz)1
Frequency (kHz)1
335
330
325
320
315
310
305
300
4
6
8
10
12
14
335
330
325
320
315
310
V
IN
= 4.5V
V
IN
= 12V
V
IN
= 23V
V
OUT
= 3.3V, I
OUT
= 0A
16
18
20
22
24
305
300
-50
-25
0
25
V
OUT
= 3.3V, I
OUT
= 0A
50
75
100
125
Input Voltage (V)
Copyright
©
2016 Richtek Technology Corporation. All rights reserved.
Temperature (
C)
is a registered trademark of Richtek Technology Corporation.
DS8290-04
October 2016
www.richtek.com
5
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