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PDF US3027 Data sheet ( Hoja de datos )
| Número de pieza | US3027 | |
| Descripción | 5 BIT PROGRAMMABLE SYNCHRONOUS BUCK PLUS TRIPPLE LDO CONTROLLER | |
| Fabricantes | UNISEM | |
| Logotipo |  |
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US3027
5 BIT PROGRAMMABLE SYNCHRONOUS BUCK
FEATURES
PLUS TRIPPLE LDO CONTROLLER
PRELIMINARY DATASHEET
DESCRIPTION
Designed to meet VRM 9.0 specification for
next generation micrprocessors
On board 5 bit DAC programs the output
voltage from 1.075V to 1.850V in 25mV steps
Linear regulator controller on board for 1.8V
Provides Single Chip Solution for Vcore,
GTL+ ,AGP Bus, and 1.8V
Automatic Voltage Selection for AGP slot
Vddq supply
Linear regulator controller on board for 1.5V
GTL+ supply
Loss less Short Circuit Protection for all
outputs
Synchronous operation allows maximum
efficiency
Patented architecture allows fixed frequency
operation as well as 100% duty cycle during
dynamic load
Minimum part count
Soft Start
High current totem pole driver for direct
driving of the external Power MOSFET
Power Good function Monitors all Outputs
OVP Circuitry Protects the Switcher Output
and generates a Fault output
APPLICATIONS
Total Power Soloution for Next Generation Intel
Processor application
AMD K7 Low Cost Solution
The US3027 controller IC is specifically designed to meet
VRM 9.0 specification for next generation microproces-
sor applications requiring multiple on board regulators .
The US3027 provides a single chip controller IC for
the Vcore , 3LDO controllers, one with the auto-
matic select pin that connects to the TYPE DETECT
pin of the AGP slot for the AGP Vddq supply, one
for GTL+ and the other for the 1.8V chip set regula-
tor as required for the next generation PC applica-
tions. The US3027 is designed to use either Bipolar
transistors for Vout3(1.5V) and Vout4(1.8V) or if Vaux
pin is connected to 12V, then MOSFETs can also be
used as external pass elements. No external resis-
tor divider is necessary for any of the regulators.
The switching regulator feature a patented topology that
in combination with a few external components as shown
in the typical application circuit ,will provide well in ex-
cess of 20A of output current for an on- board DC/DC
converter while automatically providing the right output
voltage via the 5 bit internal DAC .The US3027 also fea-
tures, loss less current sensing for both switcher by
using the Rds-on of the high side Power MOSFET
as the sensing resistor, an output under voltage
shutdown that detects short circuit condition for the
linear outputs and latches the system off, and a
Power Good window comparator that switches its open
collector output low when any one of the outputs is out-
side of a pre programmed window.
TYPICAL APPLICATION
5V
3.3V
Vout2
LINEAR
CONTROL
US3027
SWITCHER
CONTROL
Vout1
Vout3
LINEAR
CONTROL
LINEAR
CONTROL
3027app3-1.0
Vout4
PACKAGE ORDER INFORMATION
Ta (°C)
0 TO 70
Device
US3027CW
Rev. 1.3
12/8/00
Package
28 pin Plastic SOIC WB
4-1
1 page  
US3027
PIN# PIN SYMBOL
22 Vsen1
10 Vsen2
15 Drive4
23 OCSET
26 PHASE
12 SS
13 FAULT/Rt
18 Drive3
19 Vsen3
16 NC
Pin Description
This pin is internally connected to the undervoltage and overvoltage comparators sensing
the Vcore status. It must be connected directly to the Vcore supply.
This pin provides the feedback for the AGP linear regulator. The Select pin when con-
nected to the "Type Detect" pin of the AGP slot automatically selects the right voltage for
the AGP Vddq.
This pin controls the gate of an external MOSFET for the 1.8V chip set linear regulator.
This pin is connected to the Drain of the power MOSFET of the Core supply and it
provides the positive sensing for the internal current sensing circuitry. An external resis-
tor programs the C.S threshold depending on the Rds of the power MOSFET. An external
capacitor is placed in parallel with the programming resistor to provide high frequency
noise filtering.
This pin is connected to the Source of the power MOSFET for the Core supply and it
provides the negative sensing for the internal current sensing circuitry.
This pin provides the soft start for all the regulators. An internal current source charges
an external capacitor that is connected from this pin to GND which ramps up the outputs
of the regulators, preventing the outputs from overshooting as well as limiting the input
current. The second function of the Soft Start cap is to provide long off time (HICCUP) for
the synchronous MOSFET during current limiting.
This pin has dual function. It acts as an output of the OVP circuitry or it can be used to
program the frequency using an external resistor . When used as a fault detector, if any
of the switcher outputs exceed the OVP trip point, the FAULT pin switches to 12V and
the soft start cap is discharged. If the FAULT pin is to be connected to any external
circuitry, it needs to be buffered.
This pin controls the gate of an external transistor for the 1.5V GTL+ linear regulator.
This pin provides the feedback for the linear regulator that its output drive is Drive3.
This pin is NO connect.
14 Vsen4
17 GND
24 PGND
25 LGATE
27 UGATE
28 V12
20 V5
11 Select
2 FIX
This pin provides the feedback for the linear regulator that its output drive is Drive4.
This pin serves as the ground pin and must be connected directly to the ground plane.
This pin serves as the Power ground pin and must be connected directly to the GND
plane close to the source of the synchronous MOSFET. A high frequency capacitor
(typically 1 uF) must be connected from V12 pin to this pin for noise free operation.
Output driver for the synchronous power MOSFET for the Core supply.
Output driver for the high side power MOSFET for the Core supply.
This pin is connected to the 12 V supply and serves as the power Vcc pin for the output
drivers. A high frequency capacitor (typically 1 uF) must be placed close to this pin and
PGND pin and be connected directly from this pin to the GND plane for the noise free
operation.
5V supply voltage. A high frequency capacitor (0.1 to 1 uF) must be placed close to this
pin and connected from this pin to the GND plane for noise free operation.
This pin provides automatic voltage selection for the AGP switching regulator. When it is
pulled LO, the voltage is 1.5V and when left open or pulled to HI, the voltage is 3.3V.
Leaving this pin open provides fixed output voltages of the 1.5V and 1.8V for the #3 and #4
linear regulators. When this pin is grounded the reference to the linear regulators are set
to 1.26V and therefore the output of the regulators can be programmed to any voltages
above the 1.26V using; Vout=1.26*(1+Rtop/Rbot)
Where:
Rtop=Top resistor connected from the output to the Vsense pin
Rbot=Bottom resistor connected from the Vsense pin to ground.
Rev. 1.3
12/8/00
4-5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet US3027.PDF ] | |
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