RT9226A
Synchronous PWM Step-down DC/DC Converter Controller
General Description
The RT9226A is a low cost, high-efficiency voltage-
mode PWM controller for motherboard power supply
application. Synchronous N-channel MOSFET driver,
short-circuit protection, and soft start function are
integrated in a single chip. A simple high power buck
regulator with shutdown function can be
implemented with minimum external components.
The RT9226A provides current-limit protection by
monitoring the voltage drop across N-channel
MOSFET in over current condition, therefore,
eliminates the current sensing resistor and minimizes
the efficiency loss. The soft start function reduces the
stress on power supply and components in power on
duration. The 200 kHz operating frequency and high
speed PWM control loop with Synchronous N-
channel MOSFET driver provide optimized
compromise between efficiency, cost, and response
speed. Other features include output voltage
monitoring for power good indication and over
voltage protection.
Ordering Information
RT9226A-
Package type
S : SOP-14
Operating temperature range
C: Commercial standard
Features
z
Synchronous N-channel MOSFET Driver
z
High Efficiency
z
Fast Response with 200kHz Operating
Frequency
z
Adjustable Current Limit by Sensing MOSFET
r
, without Extra Current Sensing
DS(ON)
Resistor
z
Shutdown Function
z
Power Good Indication Output and Over-
voltage Protection
Applications
Low Cost CPU Power Supply
z
Motherboard I/O Power Supply
z
Add-On Card Power Supply
z
DDR SDRAM Bus Terminator Power Supply
z
Pin Configurations
Part Number Pin Configurations
RT9226ACS
(Plastic SOP-14)
VSEN
OCSET
SS
FB
EN
GND
PGNDH
1
2
3
4
5
6
7
TOP VIEW
14
13
12
11
10
9
8
VCC
LGATE
PGNDL
BOOT
UGATE
PHASE
PGOOD
DS9226A-03 July 2000 www.richtek-ic.com.tw
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RT9226A
Absolute Maximum Ratings
Supply Voltage 15V
z
Input, Output or I/O Voltage GND–0.3V to Vcc+0.3V
z
Ambient Temperature Range 0°C to 70°C
z
Operating Junction Temperature Range 0°C to 125°C
z
Storage Temperature Range −65°C to 150°C
z
Package Thermal Resistance
z
SOP-14, θ
Lead Temperature (Soldering, 10 sec.) 260°C
z
Electrical Characteristics
(V
= 12V, GND = 0V, TA = 25°C, unless otherwise specified)
CC
VCC Supply Current
160°C/W
JA
Parameter Symbol Test Conditions Min Typ Max Units
Nominal Supply Current
I
CC
UGATE Open
--
3--mA
Power-On Reset
VCC Rising Threshold V
VCC Falling Threshold V
Enable Input Threshold
V
EN
OCSET
OCSET
= 4.5V
= 4.5V
-- 9.5 -- V
-- 7.5 -- V
0.2 -- 2.2 V
Oscillator
Frequency 170 200 230
Ramp Amplitude
∆V
OSC
Internal Voltage Reference
Reference Voltage
V
REF
PWM Controller Error Amplifier
DC Gain -- 65 --
PWM Controller Gate Driver
UGATE Source
UGATE Sink
LGATE Source
LGATE Sink
R
UGATEIUGATE
R
UGATEIUGATE
I
LGATEVCC
R
LGATEILGATE
= 0.3A
= 0.3A
= 12V, V
= 1V
LGATE
= 6V
Protection
-- 1.9 --
1.225 1.250 1.275
-- 8 --
-- 6 --
-- 500 --
-- 5 --
KHz
V
V
dB
Ω
Ω
mA
Ω
OCSET Sink Current
SS Current
I
OCSETVOCSET
I
SS
VSS = 1.5V
= 4.5V
Over-voltage Trip (VSEN/VREF) -- 115 120
170 200 230
-- 10 --
µA
µA
%
To be continued
www.richtek-ic.com.tw DS9226A-03 July 2000
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Power Good
RT9226A
Parameter Symbol Test Conditions Min Typ Max Units
Upper Threshold (VSEN/VREF) -- 108 --
Lower Threshold (VSEN/VREF) -- 92 --
PGOOD Voltage Low
V
PGOODIPGOOD
= -5mA
-- 0.5 --
Function Block Diagram
EN
SS
GND
FB
PGOOD
VSEN
4.5V
47K
10µA
Vref
Ω
Output
Voltage
Monitor
Error
Amp
+
_
Soft
Start
+
+
_
PWM
Comparato r
Oscillator
Power-on
Reset
Control
Logi c
Over Current
Comparato r
Gate
Control
Logi c
200µA
_
+
VCC
OCSET
PHASE
BOOT
UGATE
PGNDH
PVCC
LGATE
PGNDL
%
%
V
DS9226A-03 July 2000 www.richtek-ic.com.tw
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RT9226A
Pin Description
Pin No. Pin Name Pin Function
1 VSEN Output voltage monitoring input
2 OCSET
Current limit set pin with 200µA current sink
3 SS Soft start, connect a capacitor from this pin to GND
4 FB Voltage-control feedback loop input
5 EN Regulator enable with low shutdown
6 GND Ground
7 PGNDH High side drive GND
8 PGOOD Power good indication output
9 PHASE Current limit sense
10 UGATE High side MOSFET driver output
11 BOOT Driver power
12 PGNDL Low side driver GND
13 LGATE Low side MOSFET driver output
14 VCC IC power
Typical Application Circuit
12V
R1
Ω
10
Low Shut down
0.1µF
D1
15VC11µF
C3
Power Good
14
5
3
12
6
7
8
BOOT
VCC
EN
SS
PGNDL
GND
PGNDH
PGOOD
RT9226A
10K 1%
11
OCSET
UGATE
PHASE
LGATE
VSEN
R5
FB
2
10
9
13
4
C2; 1000pF
R2; 2.4k
1
R4
1K 1%
C4, C5: Each 1000µF 6.3WV DC, Sanyo MV-GX or Equivalent.
L1: Core: Micrometals T50-52; Winding: 5 turns of 18 AWG.
L2: Core: Micrometals T60-52; Winding: 14 turns of 17 AWG.
Q1, Q2: CET6030L
Q1
Q2
R3
1K 1%
C6
1µF
D2
1N5817
+
C4
-
1000µF×2
L2
7µH
L1
1µH
+
C5
-
1000µF×6
VIN 5V
V
OU T
2.5V/10A
www.richtek-ic.com.tw DS9226A-03 July 2000
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Package Information
RT9226A
H
M
B
A
C
F
Dimensions In Millimeters Dimensions In Inches
Symbol
A 8.534 8.738 0.336 0.344
B 3.810 3.988 0.150 0.157
C 1.346 1.753 0.053 0.069
D
I
Min Max Min Max
B
J
D 0.330 0.508 0.013 0.020
F 1.194 1.346 0.047 0.053
H 0.178 0.254 0.007 0.010
I 0.102 0.254 0.004 0.010
J 5.791 6.198 0.228 0.244
M 0.406 1.270 0.016 0.050
14–Lead SOP Plastic Package
DS9226A-03 July 2000 www.richtek-ic.com.tw
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RT9226A
RICHTEK TECHNOLOGY CORP.
Headquarter
6F, No. 35, Hsintai Road, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5510047 Fax: (8863)5537749
www.richtek-ic.com.tw DS9226A-03 July 2000
RICHTEK TECHNOLOGY CORP.
Taipei Office (Marketing)
8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: (8862)89191466 Fax: (8862)89191465
Email: marketing@richtek-ic.com.tw
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