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PDF RT9245B Data sheet ( Hoja de datos )
| Número de pieza | RT9245B | |
| Descripción | Multi-Phase PWM Controller | |
| Fabricantes | Richtek Technology | |
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RT9245B
Multi-Phase PWM Controller for K8 CPU Core Power Supply
General Description
RT9245B is a multi-phase buck DC/DC controller
integrated with all control functions for AMD K8 CPU. The
RT9245B could be operated with 2, 3 or 4 buck switching
stages operating in interleaved phase set automatically.
The multiphase architecture provides high output current
while maintaining low power dissipation on power devices
and low stress on input and output capacitors. The high
equivalent operating frequency also reduces the
component dimension and the output voltage ripple in load
transient.
RT9245B implements both voltage and current loops to
achieve good regulation, response and power stage
thermal balance.
RT9245B applies the DCR sensing technology newly. The
RT9245B extracts the ESR of output inductor as sense
component to deliver a precise load line regulation and
good thermal balance for next generation processor
application.
Current sense setting, droop tuning, VCORE initial offset
and ov er current protection are independent on
compensation circuit of voltage loop. The feature greatly
facilitates the flexibility of CPU power supply design and
tuning. The DAC output of RT9245B supports AMD K8
6-bit VID, precise offset value & smooth VCORE transient
at VID jump. The IC monitors the VCORE voltage for PGOOD
and over-voltage protection. Soft-start, over-current
protection and programmable under-voltage lockout are
also provided to assure the safety of microprocessor and
power system. The RT9245B comes to a small footprint
package TSSOP-28.
Ordering Information
RT9245B
Package Type
C : TSSOP-28
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Features
l Multi-Phase Power Conversion with Automatic
Phase Selection
l 6-bit AMD K8 M2 DAC Output with Active Droop
Compensation for Fast Load Transient
l Smooth VCORE Transition at VID Jump
l Power Stage Thermal Balance by DCR Current
Sense
l Hiccup Mode Over-Current Protection
l Programmable Switching Frequency (50kHz to
400kHz per Phase), Under-Voltage Lockout and Soft-
Start
l High Ripple Frequency Times Channel Number
l 28-TSSOP Package
l RoHS Compliant and 100% Lead (Pb)-Free
Applications
l AMD K8 Processors Voltage Regulator
l Low Output Voltage, High Current DC-DC Converters
l Voltage Regulator Modules
Pin Configurations
(TOP VIEW)
VID4
VID3
VID2
VID1
VID0
VID5
SGND
FB
COMP
PGOOD
DVD
SS
RT
VOSS
2
3
4
5
6
7
8
9
10
11
12
13
14
28 VCC
27 PWM1
26 PWM2
25 PWM3
24 PWM4
23 CSP4
22 CSP2
21 CSP3
20 CSP1
19 GND
18 ADJ
17 IOUT
16 CSN
15 IMAX
TSSOP-28
Note :
RichTek Pb-free and Green 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.
}100% matte tin (Sn) plating.
DS9245B-02 March 2007
www.richtek.com
1
1 page  
VID5
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
VID4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
RT9245B
VID3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
Table 1. Output Voltage Program
Pin Name
VID2
VID1
VID0
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
000
001
Nominal Output Voltage DACOUT
1.5500
1.5250
1.5000
1.4750
1.4500
1.4250
1.4000
1.3750
1.3500
1.3250
1.3000
1.2750
1.2500
1.2250
1.2000
1.1750
1.1500
1.1250
1.1000
1.0750
1.0500
1.0250
1.0000
0.9750
0.9500
0.9250
0.9000
0.8750
0.8500
0.8250
0.8000
0.7750
0.7625
0.7500
To be continued
DS9245B-02 March 2007
www.richtek.com
5
5 Page 
Application Information
RT9245B is a multi-phase DC/DC controller that precisely
regulates CPU core voltage and balances the current of
different power channels. The converter consisting of
RT9245B and its companion MOSFET driver RT9619
provides high quality CPUpower and all protection functions
to meet the requirement of modern VRM.
Voltage Control
RT9245B senses the CPU VCORE by SGND pin to sense
the return of CPU to minimize the voltage drop on PCB
trace at heavy load. OVP is sensed at FB pin. The internal
high accuracy VIDDAC provides the reference voltage for
K8 compliance. Control loop consists of error amplifier,
multi-phase pulse width modulator, driver and power
components. As conventional voltage mode PWM
controller, the output voltage is locked at the VREF of
error amplifier and the error signal is used as the control
signal of pulse width modulator. The PWM signals of
different channels are generated by comparison of EA
output and split-phase sawtooth wave. Power stage
transforms VIN to output by PWM signal on-time ratio.
Current Balance
RT9245B senses the inductor current via inductor's DCR
for channel current balance and droop tuning. The differential
sensing GM amplifier converts the voltage on the sense
component (can be a sense resistor or the DCR of the
inductor) to current signal into internal balance circuit.
The current balance circuit sums and averages the current
signals and then produces the balancing signals injected
to pulse width modulator. If the current of some power
channel is larger than average, the balancing signal
reduces that channels pulse width to keep current balance.
The use of single GM amplifier via time sharing technique
to sense all inductor currents can reduce the offset errors
and linearity variation between GMs. Thus it can greatly
improve signal processing especially when dealing with
such small signal as voltage drop across DCR.
Droop & Load Line Setting
RT9245B injects averaged current IX into the resistor RADJ
connected to ADJ pin to generate a load-current-
dependent voltage RADJ for droop setting:
RT9245B
VADJ = 8 x IX x RADJ
VADJ is then subtracted from VID_DAC output as the real
reference voltage at non-inverting input of the error amplifier
as shown if Figure 1. Consequently, load line slope is
calculated as :
Load
Line
=
ΔVCORE
ΔICORE
=
8
x RADJ x DCR
N x RCSN
where N is the phase number of operation.
IVOSS /4
VCORE
RCSN
DAC
-
EA
+
VADJ
RADJ
8IX
Figure 1. Load Line and Offset Function
Fault Detection
The chip detects FB for over voltage and power good
detection. The “hiccup mode” operation of over current
protection is adopted to reduce the short circuit current.
The in-rush current at the start up is suppressed by the
soft start circuit through clamping the pulse width and
output voltage.
Phase Setting and Converter Start Up
RT9245B interfaces with companion MOSFET drivers (like
RT9619, RT9607 series) for correct converter initialization.
The tri-state PWM output (high, low and high impedance)
senses its interface voltage when IC POR acts (both VCC
and DVD trip). The channel is enabled if the pin voltage is
1.2V less than VCC. Tie the PWM to VCC and the
corresponding current sense pins to GND or left float if
the channel is unused. For example, for 3-Channel
application, connect PWM4 high.
Current Sensing Setting
RT9245B senses the current flowing through inductor via
its DCR for channel current balance and droop tuning.
DS9245B-02 March 2007
www.richtek.com
11
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet RT9245B.PDF ] | |
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