RICHTEK RT9224ECS Datasheet
Preliminary
RT9224E
VRM 8.5 Synchronous PWM Buck Converter
Controller and Output Voltage Monitor
General Description
The RT9224E is a high speed switching controller
designed for use in Synchronous DC/DC buck
converter for modern CPUs. The regulated output
voltage is digitally programmable from 1.05V to
1.825V by a 5-bit DAC which provides initial
accuracy of ±1%. The RT9224E drives two external
N-channel MOSFETs, providing high efficiency and
eliminating the need for high cost P-channel devices.
It senses the output current across the on-resistance
of the N-channel MOSFET and provides an
adjustable current limit without external sense
resistor.
RT9224E monitors the output voltage and provides
the output signal for power-good and over-voltage
protections. The switching frequency is 200kHz. The
high switching frequency cooperating with a high
speed error amplifier maintains a fast response to
the dynamic load of modern CPUs.
Ordering Information
RT9224E
Package type
S : SOP-20
Operating temperature range
C: Commercial standard
Features
z
Simple Voltage-mode PWM Control with Buck
Rectification
z ±
±1% DAC Output Voltage Accuracy
±±
z
5-Bit Digital-to-Analog Output Voltage Range
from 1.05V to 1.825V
z
Fast Transient Response and Excellent Output
Voltage Regulation
z
Fault Protection for Over-voltage and Over-
current
z
Power-good Output Voltage Monitor
Applications
Power Supply for VRM 8.5 Microprocessors
z
Low-voltage Distributed Power Supplies
z
High Power 5V to 1.05V ~ 1.85V Switching
z
Regulator
Pin Configurations
Part Number Pin Configurations
RT9224ECS
(Plastic SOP-20)
VSEN
OCSET
SS
VID25
VID0
VID1
VID2
VID3
NC
FB
TOP VIEW
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
NC
OVP
VCC
LGATE
PGND
BOOT
UGATE
PHASE
PGOOD
GND
DS9224E-01 May 2001 www.richtek-ic.com.tw
1
RT9224E
Preliminary
Absolute Maximum Ratings
z Supply Voltage +15V
z Boot Voltage +15V
z Input, Output or I/O Voltage GND – 0.3V to V
z Storage Temperature Range –65°C ~150°C
z Package Thermal Resistance
SOP-20, θ
JA
87°C/W
+ 0.3V
CC
Recommended Operating Conditions
z Supply Voltage +12V±10%
z Ambient Temperature Range 0°C to 70°C
z Junction Temperature Range 0°C
to 125°C
Electrical Characteristics
(TA = 25°C, recommended operating conditions, unless otherwise specified)
Parameter Symbol Test Conditions Min Typ Max Units
VCC Supply Current
Nominal Supply
I
CC
UGATE and LGATE -- 3 -- mA
Power-on Reset
VCC Rising Threshold
VCC Falling Threshold
Rising V
OCSET
Threshold
V
OCSET
V
OCSET
= 4.5V
= 4.5V
-- 9.5 -- V
-- 7.5 -- V
-- 1.6 -- V
Oscillator
Free Running Frequency 170 200 230 KHz
Ramp Amplitude
∆V
OSC
-- 1.9 -- V
P-P
Reference and DAC
DAC (VID0-VID25) Input Low Voltage -- -- 0.8 V
DAC (VID0-VID25) Input High Voltage 2.0 -- -- V
DACOUT Voltage Accuracy -1.0 -- +1.0 %
Error Amplifier
DC Gain -- 65 -- dB
Gate Drivers
UGATE Source
UGATE Sink
LGATE Source
LGATE Sink
R
UGATEVBOOT
R
UGATEVUGATE
I
LGATE
R
LGATEVLGATE
VCC = 12V, VLGATE = 6V
– V
– V
= 1V
PHASE
PHASE
= 12V
= 1V
-- 8 --
-- 5 --
-- 500 --
-- 5 --
Ω
Ω
mA
Ω
To be continued
www.richtek-ic.com.tw DS9224E-01 May 2001
2
Preliminary
RT9224E
Parameter Symbol Test Conditions Min Typ Max Units
Protection
Over-voltage Trip (VSEN/DACOUT) -- 115 120 %
OCSET Current Source
OVP Sourcing Current
Soft-Start Current
I
OCSET
I
OVP
I
SS
V
OCSET
V
SEN
V
SS
= 4.5V
= 5.5V, V
= 1.5V
OVP
= 0V
167 200 233
60 -- -- mA
-- 10 --
Power Good
Upper Threshold (VSEN/DACOUT) VSEN Rising 106 -- 114 %
Lower Threshold (VSEN/DACOUT) VSEN Falling 89 -- 96 %
Hysteresis (VSEN/DACOUT) Upper and Lower Threshold -- 2 -- %
PGOOD Voltage Low
V
PGOOD
I
CPGOOD
= -5mA
-- 0.5 -- V
Function Block Diagram
VCC
VSEN
OCSET
REFE RENCE
110%
90%
115%
200µA
+
_
+
_
OVER-
VOLTAGE
+
_
+
_
OVER-
CURRENT
4. 5V
POWER-ON
RESET (POR)
SOFTSTART
PGOOD
OVP
10µA
SS
BOOT
UGATE
µA
µA
PHASE
LG ATE
PGND
GND
_
INHIBIT
GATE
CONTROL
LO GIC
PWM
VID0
VID1
VID2
VID3
VID25
FB
DS9224E-01 May 2001 www.richtek-ic.com.tw
TTL D/A
CONVERTER
(DAC)
DACO UT
ERRO R
AMP
+
OSCILLATOR
PWM
COMPARATOR
+
_
3
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