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PDF RT9246 Data sheet ( Hoja de datos )
| Número de pieza | RT9246 | |
| Descripción | Multi-Phase PWM Controller | |
| Fabricantes | Richtek Technology | |
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RT9246
Multi-Phase PWM Controller for CPU Core Power Supply
General Description
The RT9246 is a multi-phase buck DC/DC controller
integrated with all control functions for GHz CPU VRM.
The RT9246 controls 2 or 3 buck switching stages
operating in interleaved phase set automatically. The multi-
phase 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.
RT9246 controls both voltage and current loops to achieve
good regulation, response & power stage thermal balance.
Precise current loop using RDS(ON) as sense component
builds precise load line for strict VRM DC & transient
specification and also ensures thermal balance of different
power stages. The settings of current sense, droop tuning,
VCORE initial offset and over current protection are
independent to compensation circuit of voltage loop. The
feature greatly facilitates the flexibility of CPU power supply
design and tuning.
The DAC output of RT9246 supports K8 CPU by 5-bit VID
input, precise initial 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.
Ordering Information
RT9246
Package Type
C : TSSOP-28
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
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.
DS9246-06 March 2007
Features
z Multi-Phase Power Conversion with Automatic
Phase Selection
z K8 DAC Output with Active Droop Compensation
for Fast Load Transient
z Smooth VCORE Transition at VID Jump
z Power Stage Thermal Balance by RDS(ON) 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 RoHS Compliant and 100% Lead (Pb)-Free
Applications
z AMD® AthlonTM 64 and OpteronTM Processors Voltage
Regulator
z Low Output Voltage, High Current DC-DC Converters
z Voltage Regulator Modules
Pin Configurations
(TOP VIEW)
VID4
VID3
VID2
VID1
VID0
SS2
SGND
FB
COMP
PGOOD
DVD
SS
RT
VOSS
28
2 27
3 26
4 25
5 24
6 23
7 22
8 21
9 20
10 19
11 18
12 17
13 16
14 15
TSSOP-28
VCC
PWM1
PWM2
PWM3
ISN1
ISP1
ISP2
ISP3
ISN23
GND
ADJ
VDIF
VSEN
IMAX
www.richtek.com
1
1 page  
RT9246
Table 1. Output Voltage Program
VID4
0
VID3
0
VID2
0
VID1
0
VID0
0
Nominal Output Voltage DACOUT
1.550
00001
1.525
00010
1.500
00011
1.475
00100
1.450
00101
1.425
00110
1.400
00111
1.375
01000
1.350
01001
1.325
01010
1.200
01011
1.275
01100
1.250
01101
1.225
01110
1.200
01111
1.175
10000
1.150
10001
1.125
10010
1.100
10011
1.075
10100
1.050
10101
1.025
10110
1.000
10111
0.975
11000
0.950
11001
0.925
11010
0.900
11011
0.875
11100
0.850
11101
0.825
11110
0.800
11111
Shutdown
Note: (1) 0 : Connected to GND
(2) 1 : Open
DS9246-06 March 2007
www.richtek.com
5
5 Page 
RT9246
Application Information
RT9246 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
RT9246 and its companion MOSFET driver provides high
quality CPU power and all protection functions to meet
the requirement of modern VRM.
Voltage Control
RT9246 senses the CPU VCORE by an precise instrumental
amplifier to minimize the voltage drop on PCB trace at
heavy load. VSEN & SGND are the differential inputs. VDIF
is the output node of the differential voltage & the input for
PGOOD & OVP sense. The internal high accuracy VID
DAC provides the reference voltage for K8 compliance.
Control loop consists of error amplifier, multi-phase pulse
width modulator, driver and power components. Like
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 VC 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
RT9246 senses the current of low side MOSFET in each
synchronous rectifier when it is conducting 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 RDS(ON) of the low side
MOSFET) to current signal into internal balance circuit.
The current balance circuit sums and averages the current
signals then produces the balancing signals injected to
pulse width modulator. If the current of some power
channel is greater than average, the balancing signal
reduces the output pulse width to keep the balance.
Load Droop
The sensed power channel current signals regulate the
reference of DAC to form a output voltage droop
proportional to the load current. The droop or so-called
“active voltage positioning” can reduce the output voltage
ripple at load transient and the LC filter size.
DS9246-06 March 2007
Fault Detection
The chip detects VCORE for over voltage and power good
detection. The “hiccup mode” operation of over-current
protection is adopted to reduce the short circuit current.
The inrush 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
RT9246 interfaces with companion MOSFET drivers (like
RT9600, RT9602 or RT9603 series) for correct converter
initialization. The tri-state PWM output (high, low and high
impedance) pins sense the interface voltage at IC POR
period (both VCC and DVD trip). The channel is enabled if
the pin voltage is 1.2V less than VCC. Please tie the PWM
output to VCC and the current sense pins to GND or left
floating if the channel is unused. For 2-Channel application,
connect PWM3 high.
Current Sensing Setting
RT9246 senses the current of low side MOSFET in each
synchronous rectifier when it is conducting 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 RDS(ON) of the low side
MOSFET) to current signal into internal circuit (see
Figure 1). Be careful to choose GND sense input, ISN, of
the GM amplifier for effective channel current balance.
Current
< Balance
IX
< Droop Tune 2IX
< IX
Over-Current
Detection
Sample
&
Hold
Current
< Balance
IX
< Droop Tune 2IX
< IX
Over-Current
Detection
Current
< Balance
IX
< Droop Tune 2IX
< IX
Over-Current
Detection
Sample
&
Hold
Sample
&
Hold
IX1
IBP
-
GM
+
IBN
IX2
IBP
-
GM
+
IBN
IBN
+
GM
-
IBP
IX3
ISP1 RSP1
ISN1
RS
RSN1
IL
ISP2 RSP2
RS
ISN23 RSN23
Channel 2 & 3
GND return
ISP3
RSP3
IL
RS
IL
Figure 1. Current Sense Circuit
www.richtek.com
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet RT9246.PDF ] | |
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