US3021B
5 BIT PROGRAMMABLE SYNCHRONOUS BUCK
PLUS TRIPPLE LDO CONTROLLER
PRELIMINARY DATASHEET
FEATURES
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 1.8V
Designed to meet Intel Latest VRM specifica-
tion for next generation micrprocessors
On board DAC programs the output voltage
from 1.3V to 3.5V
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
DESCRIPTION
The US3021B controller IC is specifically designed to
meet Intel specification for next generation micropro-
cessor applications requiring multiple on board regula-
tors .
The US3021B provides a single chip control-
ler IC for the Vcore , 3LDO controllers, one with the
automatic select pin that connects to the TYPE DE-
TECT pin of the AGP slot for the AGP Vddq supply,
one for GTL+ and the other for the 1.8V chip set
regulator as required for the next generation PC
applications. The US3021B typically uses Bipolar
transistors for Vout3(1.5V) and Vout4(1.8V) however
if Vaux pin is connected to 12V, then MOSFETs can
also be used as external pass elements. No exter-
nal resistor divider is necessary for any of the regu-
lators.
The switching regulator feature a patented topol-
ogy that in combination with a few external components
as shown in the typical application circuit ,will provide
well in excess 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 US3021B
also features,
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 condi-
tion 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 out-
puts is outside of a pre programmed window.
APPLICATIONS
Total Power Soloution for Next Generation Intel
Processor application
TYPICAL APPLICATION
5V
3.3V
LINEAR
CONTROL
SWITCHER
CONTROL
Vout1
Vout2
US3021B
LINEAR
CONTROL
Vout3
LINEAR
CONTROL
Vout4
3021Bapp3-1.1
PACKAGE ORDER INFORMATION
Ta (°C)
0 TO 70
Rev. 1.4
12/8/00
Device
US3021BCW
Package
28 pin Plastic SOIC WB
4-1
US3021B
ABSOLUTE MAXIMUM RATINGS
V5 supply Voltage ........................................... 7V
V12 Supply Voltage ............................................ 20V
Storage Temperature Range ................................. -65 TO 150
°
C
Operating Junction Temperature Range .......... 0 TO 125
°
C
PACKAGE INFORMATION
28 PIN WIDE BODY PLASTIC SOIC (W)
TOP VIEW
Drive2
1
Fix
2
VID4
3
VID3
4
VID2
5
VID1
6
VID0
7
PGood
8
SD
9
Vsen2
10
Select
11
SS
12
Fault / Rt
13
Vsen4
14
28
V12
27
UGate
26
Phase
25
LGate
24
PGnd
23
OCSet
22
Vsen1
21
Fb
20
V5
19
Vsen3
18
Drive3
17
Gnd
16
Vaux
15
Drive4
θ
JA
=80°C/W
ELECTRICAL SPECIFICATIONS
Unless otherwise specified ,these specifications apply over ,V12 = 12V, V5 = 5V and Ta=0 to 70°C. Typical values
refer to Ta =25°C. Low duty cycle pulse testing are used which keeps junction and case temperatures equal to the
ambient temperature.
PARAMETER
SYM TEST CONDITION
MIN
TYP
MAX
UNITS
Supply UVLO Section
UVLO Threshold-12V
Supply ramping up
10
V
UVLO Hysterises-12V
0.6
V
UVLO Threshold-5V
Supply ramping up
4.4
V
UVLO Hysterises-5V
0.3
V
Supply Current
Operating Supply Current
V12
6
mA
V5
30
Switching Controllers; Vcore (Vsen 1) and AGP (Vsen 2)
VID Section (Vcore only)
DAC output voltage (note 1)
0.99Vs Vs
1.01Vs V
DAC Output Line Regulation
0.1
%
DAC Output Temp Variation
0.5
%
VID Input LO
0.8
V
VID Input HI
2
V
VID input internal pull-up
resistor to V5
27
kΩ
Vsen2 Voltage
Select<0.8V
1.5
V
Select>2V
3.3
V
4-2
Rev. 1.4
12/8/00
US3021B
Error Comparator Section
Input bias current
Input Offset Voltage
Delay to Output
Current Limit Section
C.S Threshold Set Current
C.S Comp Offset Voltage
Hiccup Duty Cycle
Output Drivers Section
Rise Time
Fall Time
Dead band Time Between
High side and Synch Drive
(Vcore Switcher Only)
Oscillator Section (internal)
Osc Frequency
1.8V Regulator (Vsen 4)
Vsense Voltage
Vo4
Vsense Voltage
Input bias current
Output Drive Current
1.5V Regulator (Vsen 3)
Vsense Voltage
Vsense Voltage
Input bias current
Output Drive Current
Power Good Section
Vsen1 UV lower trip point
Vsen1 UV upper trip point
Vsen1 UV Hysterises
Vsen1 HV upper trip point
Vsen1 HV lower trip point
Vsen1 HV Hysterises
Vsen2 trip point
Vsen4 trip point
Vsen3 trip point
Power Good Output LO
Power Good Output HI
Fault (Overvoltage) Section
Core O.V. upper trip point
Core O.V. lower trip point
FAULT Output HI
Soft Start Section
Soft Start Current
2
+2
100
200
-5
Css=0.1 uF
CL=3000pF
CL=3000pF
10
70
70
+5
uA
mV
nS
uA
mV
%
nS
nS
-2
Vdiff=10mV
CL=3000pF
Rt=Open
Ta=25, Drive4 = Vsen4
200
217
1.800
1.800
2
50
nS
Khz
V
V
uA
mA
Vaux-Vdrive>0.6V
Vo3
Ta=25, Drive3 = Vsen3
1.500
1.500
2
50
Vaux-Vdrive>0.6V
V
V
uA
mA
Vsen1 ramping down
Vsen1 ramping up
Vsen1 ramping up
Vsen1 ramping down
Select<0.8V
Select>2V
Fix=GND
Fix=Open
Fix=GND
Fix=Open
RL=3mA
RL=5K pull up to 5V
Vsen1 ramping up
Vsen1 ramping down
Io=3mA
OCset=0V , Phase=5V
0.90Vs
0.92Vs
.02Vs
1.10Vs
1.08Vs
.02Vs
1.100
2.560
0.920
1.320
0.920
1.140
0.4
4.8
1.17Vs
1.15Vs
10
20
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
uA
Rev. 1.4
12/8/00
4-3
US3021B
Note 1: Vs refers to the set point voltage given in Table 1.
D4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
D3
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
D2
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
D1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
D0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
Vs
1.30
1.35
1.40
1.45
1.50
1.55
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.05
D4
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
D3
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
D2
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
D1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
D0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
Vs
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
3.4
3.5
Table 1 - Set point voltage vs. VID codes
PIN DESCRIPTIONS
PIN# PIN SYMBOL
7
VID0
Pin Description
LSB input to the DAC that programs the output voltage. This pin is TTL compatible that
realizes a logic “1” as either HI or Open. When left open,his pin is pulled up internally by
a 27kΩ resistor to 5V supply.
Input to the DAC that programs the output voltage. This pin is TTL compatible that real-
izes a logic “1” as either HI or Open. When left open,his pin is pulled up internally by a
27kΩ resistor to 5V supply.
Input to the DAC that programs the output voltage. This pin is TTL compatible that real-
izes a logic “1” as either HI or Open. When left open,his pin is pulled up internally by a
27kΩ resistor to 5V supply.
MSB input to the DAC that programs the output voltage. This pin is TTL compatible that
realizes a logic “1” as either HI or Open. When left open,his pin is pulled up internally by
a 27kΩ resistor to 5V supply.
This pin selects a range of output voltages for the DAC.When in the LOW state the range
is 1.3V to 2.05V and when it switches to HI state the range is 2.0V to 3.5V. This pin is
TTL compatible that realizes a logic “1” as either HI or Open. When left open,his pin is
pulled up internally by a 27kΩ resistor to 5V supply.
This pin is an open collector output that switches LO when any of the outputs are outside
of the specified under voltage trip point. It also switches low when Vsen1 pin is more than
10% above the DAC voltage setting.
This pin provides the feedback for the synchronous switching regulator. Typically this pin
can be connected directly to the output of the switching regulator. However, a resistor
divider is recommended to be connected from this pin to vout1 and GND to adjust the
output voltage for any drop in the output voltage that is caused by the trace resistance.
The value of the resistor connected from Vout1 to FB1 must be less than 1000Ω.
This pin controls the gate of an external MOSFET for the AGP linear regulator.
This pin provides shutdown for all the regulatos. A TTL compatible, logic level high applied
to this pin disables all the outputs and discharges the soft start capacitor. The SD signal
turns off the synchronous allowing body diode to conduct and discharge the output cap.
6
VID1
5
VID2
4
VID3
3
VID4
8
PGOOD
21
FB
1
9
Drive2
SD
4-4
Rev. 1.4
12/8/00
US3021B
PIN# PIN SYMBOL
22
Vsen1
10
Vsen2
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 normally connected to 3.3V or 5V input. When connected to the 12V supply,
it provides gate drive voltage for the # 3 and #4 (Drive 3 and 4) linear regulator's pass
transistors in case MOSFET transistors are being used instead of Bipolars.
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.
15
23
Drive4
OCSET
26
12
PHASE
SS
13
FAULT/Rt
18
19
16
Drive3
Vsen3
Vaux
14
17
24
Vsen4
GND
PGND
25
27
28
LGATE
UGATE
V12
20
11
2
V5
Select
FIX
Rev. 1.4
12/8/00
4-5
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