®
RT8284N
2A, 23V, 340kHz Synchronous Step-Down Converter
General Description
The RT8284N 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 RT8284N'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 RT8284N 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
RT8284N is a available in a SOP-8 and SOP-8
(Exposed Pad) package.
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
RT8284N
Package Type
S : SOP-8
SP: SOP-8 (Exposed Pad-Option 1)
Lead Plating System
G : Green (Halogen Free and Pb Free)
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
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
Marking Information
RT8284NGS
RT8284NGS : Product Number
SS
EN
COMP
FB
RT8284N
GSYMDNN
YMDNN : Date Code
SOP-8
BOOT
8
2
3
4
SS
EN
COMP
FB
RT8284NGSP
RT8284NGSP : Product Number
VIN
SW
GND
GND
9
7
6
5
RT8284N
GSPYMDNN
YMDNN : Date Code
SOP-8 (Exposed Pad)
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8284N-03 May 2012
www.richtek.com
1
RT8284N
Typical Application Circuit
V
IN
4.5V to 23V
2
C
IN
10µF
R
EN
100k
VIN
BOOT
RT8284N
SW 3
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
C
SS
0.1µF
4, 9 (Exposed Pad)
C
P
Open
Recommended Component Selection
V
OUT
(V) R1 (kΩ) R2 (kΩ) R
C
(kΩ)
8
76.8
10
27
5
45.3
10
20
3.3
26.1
10
13
2.5
16.9
10
9.1
1.8
9.53
10
5.6
1.2
3
10
3.6
C
C
(nF)
3.3
3.3
3.3
3.3
3.3
3.3
L (μH)
22
15
10
6.8
4.7
3.6
C
OUT
(μF)
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
22 x 2
Functional Pin Description
Pin No.
SOP-8
1
2
3
4
SOP-8
(Exposed Pad)
1
2
3
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 RT8284N 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 15.5ms .
is a registered trademark of Richtek Technology Corporation.
BOOT
VIN
SW
4,
GND
9 (Exposed Pad)
5
FB
5
6
6
COMP
7
7
EN
8
8
SS
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
DS8284N-03 May 2012
RT8284N
Function Block Diagram
VIN
Internal
Regulator
Shutdown
VA V
CC
Comparator
1.2V
+
-
Lockout
Comparator
-
2.7V
3V
6µA
SS
0.923V
+
+
-
Error Amp
COMP
+
V
CC
0.5V
Oscillator
Foldback
Control
+
Current Sense
Amplifier
Slope Comp
+
-
VA
BOOT
S
+
-
Current
Comparator
R
Q
Q
130m
Ω
SW
130m
Ω
GND
5k
EN
-
UV
Comparator
FB
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8284N-03 May 2012
www.richtek.com
3
RT8284N
Absolute Maximum Ratings
(Note 1)
−0.3V
to 25V
−0.3V
to (V
IN
+
0.3V)
−3V
to (V
IN
+
3V)
−0.3V
to 6V
−0.3V
to 6V
1.111W
Supply Voltage, VIN -----------------------------------------------------------------------------------------------
Input Voltage, SW --------------------------------------------------------------------------------------------------
<20ns -----------------------------------------------------------------------------------------------------------------
V
BOOT
−
V
SW
---------------------------------------------------------------------------------------------------------
Other Pins Voltages -----------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
SOP-8 -----------------------------------------------------------------------------------------------------------------
SOP-8 (Exposed Pad) -------------------------------------------------------------------------------------------- 1.333W
Package Thermal Resistance (Note 2)
SOP-8,
θ
JA
----------------------------------------------------------------------------------------------------------- 90°C/W
SOP-8 (Exposed Pad),
θ
JA
--------------------------------------------------------------------------------------- 75°C
SOP-8 (Exposed Pad),
θ
JC
-------------------------------------------------------------------------------------- 15°C
Junction Temperature ---------------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°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, VIN
----------------------------------------------------------------------------------------------- 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
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
ΔI
C
= ±10μA
Min
--
--
0.909
--
--
--
Typ
0.5
0.8
0.923
940
130
130
0
4.3
1.3
4
340
100
Max
3
1.2
0.937
--
--
--
10
--
--
--
380
--
Unit
μA
mA
V
μA/V
mΩ
mΩ
μA
A
A
A/V
kHz
kHz
Error Amplifier Transconductance G
EA
V
EN
= 0V, V
SW
= 0V
Min.Duty Cycle, V
BOOT−SW
= 4.8V
From Drain to Source
G
CS
f
OSC1
f
OSC2
V
FB
= 0V
--
--
--
--
300
--
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8284N-03 May 2012
RT8284N
Parameter
Maximum Duty Cycle
Minimum On-Time
EN Input Threshold
Voltage
Logic-High
Logic-Low
Symbol
Test Conditions
V
FB
= 0.7V
Min
--
--
2.7
--
V
IN
Rising
V
SS
= 0V
C
SS
= 0.1μF
3.8
--
--
--
--
Typ
93
100
--
--
4.2
320
6
15.5
150
Max
--
--
5.5
0.4
4.5
--
--
--
--
Unit
%
ns
V
V
mV
μA
ms
°C
D
MAX
t
ON
V
IH
V
IL
V
UVLO
ΔV
UVLO
I
SS
t
SS
(Note 5)
T
SD
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..
Note 5.
Guaranteed by design.
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8284N-03 May 2012
www.richtek.com
5
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