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PDF RT9256 Data sheet ( Hoja de datos )
| Número de pieza | RT9256 | |
| Descripción | Actively Alternative Mode Two-Phase / Dual Switching PWM Controller | |
| Fabricantes | Richtek Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT9256 (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
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Preliminary
RT9256
Actively Alternative Mode Two-Phase / Dual Switching
PWM Controller
General Description
The RT9256 is an analogous current mode design and is
specifically promoted for high power density consideration
platform with MLCC capacitor attached, such as high-end
add-on graphic card core power and DDR SDRAM core
power, etc. A highlight for RT9256 is the RichTek’ s new
innovation of actively alternative mode operation two-phase
power conversion or dual PWM controller operation. Based
on above innovation architecture, the RT9256 provides more
flexibility and higher performance to customer application.
The part is implemented specially for multiple power
sourcing with power budget limitation. The part comes to
small footprint package VQFN-32L 5x5.
Ordering Information
RT9256
Package Type
QV : VQFN-32L 5x5 (V-Type)
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.
Features
z Analogous Current Mode Design
z Innovative Design for Actively Alternative Mode
Operation :
`Two-Phase Power Conversion
`Dual PWM Controllers
z 2.5V to 12V Switching Source Power
z 0.8V to 3.3V Output Voltage Regulation
z Multiple Power Sourcing for Power Budget Limitation
z Adjustable VIN Feed-Forward Ramp Slope
z Adjustable Operation Frequency
z Precision Core Voltage Regulation
z Precision DCR Current Sensing (with High Quality
Capacitor, X7R)
z ±1% VREF Accuracy
z Input Voltage : 12V or 5V Bias
z Enable and PGOOD Function for Sequencing-
Concerned Power
z Over Current Protection
z Over Voltage Protection
z External Soft Start Setting
z Operation Frequency Up to 1.0MHz Per Channel
z 32-Lead VQFN Package
z RoHS Compliant and 100% Lead (Pb)-Free
Pin Configurations
(TOP VIEW)
Applications
z Add-on graphic core power card
z DDR SDRAM core power
z Gaming Console
z High power density consideration platform
z Desktop/motherboard high power devices
z Power sequencing-concerned power application
www.DataSheet4U.com
32 31 30 29 28 27 26 25
CSN1
CSP1
COMP1
FB1
FB2
COMP2
1
2
3
4
5
6
24 PHASE1
23 PGND
22 LGATE1
21 PVCC
20 PVCC
19 LGATE2
CSP2 7
CSN2 8
33 18 PGND
17 PHASE2
9 10 11 12 13 14 15 16
DS9256-07 August 2007
VQFN-32L 5x5
www.richtek.com
1
1 page  
Preliminary
RT9256
Out-of-phase switching in both two-phase and two-switcher
modes reduces the input current ripple and therefore
reduces the component requirement as well as cost.
The wide input voltage range of the converter ranges from
3.3V to 12V. The output voltage can be set from 0.8V to
3.3V with external resistor divider. The bias voltage of the
chip is VCC5.
The IC integrates two control circuits for two synchronous
buck converters. The default mode of RT9256 is two
switcher mode. The two phase mode can be activated by
pulling FB2 pin high before POR as shown in Figure 3.
POR
FB2
2PH 2SW
Figure 3
The power sequence of RT9256 includes: 1: POR function
2: VIN power supply detection 3: EN pin setting to enable
the whole chip. 4: PG to indicate the power good condition
of the chip The chip will detect the voltage at FB pin
when SS pass Vcc5 − 1.3 and send a PG high signal if
FB > 0.6V. The power sequence of the chip is shown in
Figure 4.
EN
POR
VIN detection
Vin
SS
> VCC5 - 1.3
SSH
www.DataFSBheet4U.com
PG
> 0.6V
Figure 4
The external elements selection of RT9256 includes 1: RT
pin resister to GND to set the operation frequency of the
chip. 2: CSN pin resister to set the current gain(ratio of
inductance current IL and sensed current Ix) and current
scaling in two phase mode operation. 3: RR pin resister to
Vin to set the slope of the Vin feed forward ramp and the
effective slope compensation of current mode. 4. IMAX
pin resister to GND to set the over current level 5: capacitor
at SS pin to set the soft-start time 6. type two
compensation at COMP pin.
Power on reset
The POR circuitry monitors the supply voltage of the chip.
When the chip power supply exceeds 4.2V, the chip
releases the reset state and works according to the
settings. Once the supply voltage is lower than 4.0V, POR
circuitry resets the chip.
VIN detection
The VIN detection circuitry monitors the switching power
source when power up. As VIN > 1.8V, RR pin is enable for
ramp setting and the chip is in ramp setting mode. The
voltage at RR pin will be about 0.55V. Otherwise, the chip
will be in VIN detection mode and RR pin is disable for
ramp setting until VIN > 1.8V. In VIN detection mode, the
UGATE and LGATE will be off and SS will be pulled low by
a constant current of 10uA. The chip will enter the ramp
setting mode and SS will re-softstart when VIN > 1.8V.
In two switcher mode, the detection function work
independently. In two phase mode, ramp setting mode will
be activated when both channel’ s VIN are ready.
Enable
After POR reset, the chip monitors the voltage of EN pin.
When VEN is higher than 0.8V, the chip is enabled. The
chip is disabled when VEN is lower than 0.8V. With a
precision threshold voltage, the EN pin can be used for
power sequence.
DS9256-07 August 2007
www.richtek.com
5
5 Page 
Preliminary
RT9256
Typical Operating Characteristics
FB Voltage vs. Input Voltage
0.81 VIN = VCC
IOUT = 0A
0.805
FB Voltage vs. Output Current
0.82 VIN = VCC = 12V
0.81
0.8 0.8
0.795
0.79
0.79
5 6 7 8 9 10 11 12
Input Voltage (V)
Switching Frequency vs. RT Resistance
1200
1000
800
600
400
200
0
0 20 40 60 80 100
RT Resistance (kΩ)
Load Transient Response
IL1 (5A/Div)
IOUT = 20 to 0A
IL2 (5A/Div)
0.78
0 2.5 5 7.5 10 12.5 15 17.5 20
Output Current (A)
Load Transient Response
IOUT = 0 to 20A
VOUT (50mV/Div)
IL1 (5A/Div)
IL2 (5A/Div)
Time (10us/Div)
Load Transient Response
IOUT = 0 to 20A
IL1 (10A/Div)
IL2 (10A/Div)
VOUT (50mV/Div)
www.DataSheet4U.com
Time (10us/Div)
VOUT (50mV/Div)
Time (200us/Div)
DS9256-07 August 2007
www.richtek.com
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet RT9256.PDF ] | |
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