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PDF RT9245 Data sheet ( Hoja de datos )
| Número de pieza | RT9245 | |
| Descripción | Multi-Phase PWM Controller | |
| Fabricantes | Richtek Technology | |
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RT9245
Multi-Phase PWM Controller for CPU Core Power Supply
General Description
RT9245 is a multi-phase buck DC/DC controller integrated
with all control functions for Intel® GHz CPU which is
VRD10.X-compliant. The RT9245 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.
RT9245 implements both voltage and current loops to
achieve good regulation, response and power stage
thermal balance.
RT9245 applies the DCR sensing technology newly. The
RT9245 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 over 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 RT9245 supports VRD10.x with
6-bit VID input, 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 RT9245 comes to a small footprint
package TSSOP-28.
Ordering Information
RT9245
Package Type
C : TSSOP-28
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Features
z Multi-Phase Power Conversion with Automatic
Phase Selection
z 6-bits VRD10.x DAC Output with Active Droop
Compensation for Fast Load Transient
z Smooth VCORE Transition at VID Jump
z Power Stage Thermal Balance by DCR Current
Sense
z Hiccup Mode Over-Current Protection
z Programmable Switching Frequency (50kHz to
400kHz per Phase), Under-Voltage Lockout and Soft-
Start
z High Ripple Frequency Times Channel Number
z 28-TSSOP Package
z RoHS Compliant and 100% Lead (Pb)-Free
Applications
z Intel® Processors Voltage Regulator : VRD10.x
z Low Output Voltage, High Current DC-DC Converters
z Voltage Regulator Modules
Pin Configurations
(TOP VIEW)
VID4
VID3
VID2
VID1
VID0
VID125
SGND
FB
COMP
PGOOD
DVD
SS
RT
VOSS
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
TSSOP-28
VCC
PWM1
PWM2
PWM3
PWM4
CSP4
CSP2
CSP3
CSP1
GND
ADJ
NC
CSN
IMAX
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.
DS9245-06 March 2007
www.richtek.com
1
1 page  
VID4
1
0
0
0
0
0
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
VID3
1
1
1
1
1
1
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
DS9245-06 March 2007
RT9245
Table 1. Output Voltage Program
VID2
1
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
0
0
0
0
Pin Name
VID1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
0
0
0
0
1
1
1
1
VID0
1
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
0
0
1
1
0
0
1
1
0
0
VID125
X
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
Nominal Output Voltage DACOUT
No CPU
0.8375V
0.850V
0.8625V
0.875V
0.8875V
0.900V
0.9125V
0.925V
0.9375V
0.950V
0.9625V
0.975V
0.9875V
1.000V
1.0125V
1.025V
1.0375V
1.050V
1.0625V
1.075V
1.0875V
1.100V
1.1125V
1.125V
1.1375V
1.150V
1.1625V
1.175V
1.1875V
1.200V
1.2125V
To be continued
www.richtek.com
5
5 Page 
Application Information
RT9245 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
RT9245 and its companion MOSFET driver RT9603/
RT9603A provides high quality CPUpower and all
protection functions to meet the requirement of modern
VRM.
Voltage Control
RT9245 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
VRD10.X 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
RT9245 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.
DS9245-06 March 2007
RT9245
Load Droop
The sensed power channel current signals regulate the
reference of DAC to form an output voltage droop
proportional to the load current. The droop or so call “active
voltage positioning” can reduce the output voltage ripple
at load transient and the LC filter size.
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
RT9245 interfaces with companion MOSFET drivers (like
RT9603, RT9602 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
RT9245 senses the current flowing through inductor via
its 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 circuit
(see Figure 1).
L =R×C
DCR
VC = DCR×IL
IX
=
VC
RCSN
L DCR
+
-
GMx
RC
RCSN
Ix
Figure 1. Current Sense Circuit
www.richtek.com
11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet RT9245.PDF ] | |
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