Page 1
Preliminary
RT9226B
Synchronous PWM Step-down DC/DC Converter Controller
General Description
The RT9226B 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 RT9226B 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
RT9226B
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
SS
FB
EN
GND
TOP VIEW
1
2
3
4
5
6
7
14
13
12
11
10
9
8
VCC
LGATE
PGNDL
BOOT
UGATE
PHASE
PGOOD
RT9226BCS
(Plastic SOP-14)
VSEN
OCSET
PGNDH
DS9226B-01 May 2001 www.richtek-ic.com.tw
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RT9226B
Preliminary
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
z
Operating Junction Temperature Range 0°C to 125°C
z
Storage Temperature Range −65°C to 150°C
z
Package Thermal Resistance
SOP-14, θ
z
Lead Temperature (Soldering, 10 sec.) 300°C
JA
160°C/W
Electrical Characteristics
(VCC = 12V, GND = 0V, TA = 25°C, unless otherwise specified)
Parameter Symbol Test Conditions Min Typ Max Units
VCC Supply Current
Nominal Supply Current
I
CC
UGATE Open -- 3 -- mA
Power-On Reset
VCC Rising Threshold
VCC Falling Threshold
Enable Input Threshold
OCSET
OCSET
= 4.5V
= 4.5V
V
V
V
EN
-- 9.5 -- V
-- 7.5 -- V
0.2 -- 2.2 V
Oscillator
Frequency 170 200 230
Ramp Amplitude
∆V
OSC
-- 1.9 --
Internal Voltage Reference
Reference Voltage
V
REF
0.785 0.800 0.815
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
-- 8 --
-- 6 --
-- 500 --
-- 5 --
Protection
KHz
V
V
dB
Ω
Ω
mA
Ω
OCSET Current Source
Soft-start Current
I
OCSETVOCSET
I
SS
VSS = 1.5V
= 4.5V
Over-voltage Trip (VSEN/VREF) -- 115 120
170 200 230
-- 10 --
µA
µA
%
Power Good
Upper Threshold (VSEN/VREF) -- 108 --
Lower Threshold (VSEN/VREF) -- 92 --
PGOOD Voltage Low
www.richtek-ic.com.tw DS9226B-01 May 2001
V
PGOODIPGOOD
= -5mA
-- 0.5 --
%
%
V
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Page 3
Function Block Diagram
Preliminary
RT9226B
EN
10µA
SS
4.5V
GND
Vref
FB
47K
Output
Voltage
Monitor
Ω
PGOOD
VSEN
Pin Description
Pin No. Pin Name Pin Function
1 VSEN Output Voltage Monitoring Input
Error
Amp
+
_
Soft
Start
+
+
_
PWM
Comparato r
Oscillator
Power-on
Reset
Control
Logi c
Over Current
Comparato r
Gate
Control
Logi c
VCC
200µA
_
+
V
CC
OCSET
PHASE
BOOT
UGATE
PGNDH
LGATE
PGNDL
2 OCSET
Current Limit Set Pin with 200µA Current Sink
3 SS Soft Start, connect a capacitor from this pin to GND
4 FB Feedback Input Pin
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 Input
10 UGATE High Side Driver Output
11 BOOT Driver Power
12 PGNDL Low Side Driver GND
13 LGATE Low Side Driver Output
14 VCC Power Supply Input
DS9226B-01 May 2001 www.richtek-ic.com.tw
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RT9226B
Typical Application Circuit
Preliminary
2
10
9
13
4
1
C2
1000 pF
R2
2. 4k
R4
910 1%
12V
R1
10
Ω
D1
15VC11µF
Low Shut dow n
C3
0. 1µF
Power Good
14
5
3
12
6
7
8
BOOT
VCC
EN
SS
PGNDL
GND
PGNDH
PGOOD
RT9226B
10K 1%
11
OCSET
UGATE
PHASE
LG ATE
FB
VSEN
R5
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: PHB83N03LT, PHB95N03LT
Q1
Q2
R3
510 1%
C6
1µF
D2
1N5817
+
C4
-
1000µF×2
L2
7µH
L1
1µH
+
C5
-
1000µF×6
VIN 5V
V
OU T
1.25V/10 A
www.richtek-ic.com.tw DS9226B-01 May 2001
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Package Information
Preliminary
RT9226B
H
M
B
A
C
F
Dimensions In Millimeters Dimensions In Inches
Symbol
Min Max Min Max
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 0.330 0.508 0.013 0.020
D
I
B
J
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
DS9226B-01 May 2001 www.richtek-ic.com.tw
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RT9226B
Preliminary
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 DS9226B-01 May 2001
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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