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IRU3072
1
Rev. 1.0
3/25/04
www.irf.com
DESCRIPTION
The IRU3072 controller IC is designed to provide a low
cost synchronous Buck regulator for on-board DC to DC
converter for multi-output applications. The outputs can
be programmed as low as 0.8V for low voltage applica-
tions.
The IRU3072 features dual soft-starts which allows power
sequencing between outputs.
Over current limit is provided by using external MOSFET's
on-resistance for optimum cost and performance.
This device features a programmable frequency set from
200KHz to 400KHz, under-voltage lockout for all input
supplies, dual external programmable soft-start functions
as well as output under-voltage detection that latches
off the device when an output short is detected.
Synchronous Controller plus 3-LDO controllers
Current Limit using MOSFET Sensing
Dual Soft-Start Function allows power sequencing
Single 5V/12V Supply Operation
Programmable Switching Frequency up to 400KHz
Fixed Frequency Voltage Mode
1A Peak Output Drive Capability
PACKAGE ORDER INFORMATION
FEATURES
20-PIN SYNCHRONOUS PWM CONTROLLER/
3 LDO CONTROLLER
APPLICATIONS
Graphic Card
DDR memory source sink V
TT
application
Applications with Multiple Outputs
Low cost on-board DC to DC such as
5V to 3.3V, 2.5V or 1.8V
Hard Disk Drive
T
A
(C)
DEVICE PACKAGE
0 To 70
IRU3072CH 20-Pin MLPQ 4x4 (H)
Data Sheet No. PD94698
Figure 1 - Typical application of IRU3072.
TYPICAL APPLICATION
IRU3072
U1
Vcc
Vc
HDrv
LDrv
Fb1
Gnd
Comp
SS1
V
OUT1
1.2V @ 8A
Rt
OCSet
PGnd
Drv4
Fb4
Drv3
Fb3
Drv2
Fb2
V
SEN33
/ SDB
SSLDO
3.3V
V
OUT2
2.5V
V
OUT3
1.8V
V
OUT4
1.5V
Q1
Q2
C2
10uF
Q3
C4
10uF
C9
10uF
C13
0.1uF
C14
33nF
C11
15nF
C7
2x 47uF,16V
C8
10uF
C12
3x 330uF, 40m
V
6TPB330M, Poscap
1uH
1uH
Q4
IRF7460
Q5
IRF7460
2.15K
R2
1K
1.25K
R4
1K
866
V
R6
1K
3.3K
46.4K
R7
VccLDO
V
IN
=12V
C5
1uF
C1
1uF
C6
0.1uF
6.81K
C10 220pF
+5V
C3
1uF
R1
R3
R5
R9
R8
L2
L1
D1
R10
499
V
R11
1K
2
Rev. 1.0
3/25/04
IRU3072
www.irf.com
ABSOLUTE MAXIMUM RATINGS
Vcc and VccLDO Supply Voltage .............................. 25V
Vc Supply Voltage .................................................... 25V
Storage Temperature Range ...................................... -65C To 150C
Operating Junction Temperature Range ..................... 0C To 125C
CAUTION: For all pins, voltage should not be below -0.5V.
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device.
PARAMETER
SYM TEST CONDITION
MIN TYP MAX UNITS
Feedback Voltage
Feedback Voltage
Fb Voltage Line Regulation
UVLO
UVLO Threshold - Vcc
UVLO Hysteresis - Vcc
UVLO Threshold - Vc
UVLO Hysteresis - Vc
UVLO Threshold - VccLDO
UVLO Hysteresis - VccLDO
UVLO Threshold - V
SEN33
UVLO Hysteresis - V
SEN33
UVLO Threshold - Fb1, 2, 3, 4
UVLO Hysteresis - Fb1, 2, 3, 4
Supply Current
Vcc Dynamic Supply Current
Vc Dynamic Supply Current
Vcc Static Supply Current
Vc Static Supply Current
5<Vcc<12
Supply Ramping Up
Supply Ramping Up
Supply Ramping Up
Supply Ramping Up
Fb Ramping Down
Freq=200KHz, C
L
=3000pF
Freq=200KHz, C
L
=3000pF
SS=0V
SS=0V
0.784
3.8
3.2
2.25
1.17
0.3
0.8
0.2
4.2
0.25
3.5
0.2
2.5
0.15
1.27
0.07
0.4
0.02
11
11
5
3
0.816
0.625
4.6
3.8
2.75
1.37
0.5
14
14
8
5
V
%
V
V
V
V
V
V
V
V
V
V
mA
mA
mA
mA
u
JA
=46
8
C/W
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
20
19
18
17
16
Fb4
Fb3
Fb2
SS
LDO
SS1
Comp
Fb1
Rt
V
S E N 3 3
/SDB
OCSet
Drv4
Drv3
Drv2
VccLDO
Vcc
LDrv
Gnd
PGnd
HDrv
Vc
PACKAGE INFORMATION
20-PIN MLPQ 4x4 (H)
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, the typical specification value applies over Vcc=5V, Vc=12V, VccLDO=5V and
T
A
=25C. the Min and Max limits apply to the temperature range from 0 to 70C. Low duty cycle pulse testing is
used which keeps junction and case temperatures equal to the ambient temperature.
V
FB
L
REG
UVLO V
CC
UVLO V
C
UVLO V
CCLDO
UVLO V
SEN33
UVLO Fb1
Dyn I
CC
Dyn I
C
I
CCQ
I
CQ
IRU3072
3
Rev. 1.0
3/25/04
www.irf.com
PARAMETER
SYM TEST CONDITION MIN TYP MAX UNITS
Soft-Start Section
Charge Current
Error Amp
Fb Voltage Input Bias Current
Fb Voltage Input Bias Current
Transconductance
Oscillator
Frequency
Ramp Amplitude
Output Drivers
Rise Time
Fall Time
Dead Band Time 1
Dead Band Time 2
Max Duty Cycle
Min Duty Cycle
LDO Controller Section
Drive Current
Fb Voltage
Input Bias Current
Thermal Shutdown
Current Limit
OC Threshold Set Current
OC Comp Off-Set Voltage
SS1=SS2=0V
SS1=3V
SS1=0V
Rt=100K
Rt=39K
Note 1
C
LOAD
=3000pF (10% to 90%)
Vcc=12V
C
LOAD
=3000pF (90% to 10%),
Vcc=12V
Vcc=12V, C
LOAD
=3000pF
HDrv falls,LDrv rises
Vcc=12V, C
LOAD
=3000pF
LDrv falls, HDrv rises
Fb=0.7V, Freq=200KHz
Fb=0.9V
Drv2, 3 and 4
Note 1
15
35
500
170
340
50
20
85
40
0.784
23
-7
25
0.1
900
200
400
1.27
50
50
115
50
92
0
60
0.8
0.5
150
30
0
m
A
m
A
m
A
m
mho
KHz
V
PP
ns
ns
ns
ns
%
%
mA
V
m
A
8
C
m
A
mV
PIN DESCRIPTIONS
Outputs of the linear regulator controllers.
This pin provides power for the LDO controllers.
This pin provides biasing for the internal blocks of the IC as well as power for the low side
driver. A minimum of 1
m
F, high frequency capacitor must be connected from this pin to
ground to provide peak drive current capability.
Output driver for the synchronous power MOSFET.
This pin serves as the ground pin and must be connected directly to the ground plane. A
high frequency capacitor (0.1 to 1
m
F) must be connected from Vcc, Vc and VccLDO pins
to this pin for noise free operation.
This pin serves as the separate ground for MOSFET's driver and should be connected to
system's ground plane.
Output driver for the high side power MOSFET. Connect a diode, such as BAT54 or 1N4148,
from this pin to ground for the application when the inductor current goes negative (Source/
Sink), soft-start at no load and for the fast load transient from full load to no load.
PIN# PIN SYMBOL PIN DESCRIPTION
1
2
3
4
5
6
7
8
9
Drv4
Drv3
Drv2
VccLDO
Vcc
LDrv
Gnd
PGnd
HDrv
35
1
75
1300
230
460
100
100
150
100
99
0.816
2
37
+7
Note 1: Guaranteed by design but not tested in production.
SS I
B1
,I
B2
I
FB1
I
FB2
Freq
V
RAMP
Tr
Tf
T
DB
D
MAX
D
MIN
I
OCSET
V
OC(OFFSET)
4
Rev. 1.0
3/25/04
IRU3072
www.irf.com
This pin is connected to a voltage that must be at least 4V higher than the bus voltage of
the switcher (assuming 5V threshold MOSFET) and powers the high side output driver. A
minimum of 1
m
F, high frequency capacitor must be connected from this pin to ground to
provide peak drive current capability.
This pin is connected to the Drain of the synchronous MOSFET and it provides the posi-
tive sensing for the internal current sensing circuitry. An external resistor programs the
current sense (CS) threshold depending on the R
DS
of the power MOSFET.
This pin is used to monitor the 3.3V rail. This pin can be pulled-low to shutdown the
outputs.
This pin sets the switching frequency with a resistor to Gnd.
This pin is connected directly to the output of the switching regulator via resistor divider to
provide feedback to the Error amplifier.
Compensation pin of the error amplifier. An external resistor and capacitor network is
typically connected from this pin to ground to provide loop compensation.
This pin provides soft-start for the switching regulator. An internal current source charges
an external capacitor that is connected from this pin to ground which ramps up the output
of the switching regulator, preventing it from overshooting as well as limiting the input
current.
This pin provides soft-start for the LDO controllers. An internal current source charges an
external capacitor that is connected from this pin to ground which ramps up the output of
the LDO controller, preventing it from overshooting as well as limiting the input current.
These pins provide feedback for the linear regulator controllers.
PIN# PIN SYMBOL PIN DESCRIPTION
10
11
12
13
14
15
16
17
18
19
20
Vc
OCSet
V
SEN33
/SDB
Rt
Fb1
Comp
SS1
SS
LDO
Fb2
Fb3
Fb4
IRU3072
5
Rev. 1.0
3/25/04
www.irf.com
BLOCK DIAGRAM
Figure 2 - Simplified block diagram of the IRU3072.
20uA
64uA
Max
POR
Oscillator
Error Amp
Ct
Error Comp
64uA
3
25K=1.6V
When SS=0
Reset Dom
POR
0.4V
FbLo Comp
Vc
HDrv
Vcc
LDrv
PGnd
SS1
Fb1
Comp
25K
3V
R
S
Q
Rt
Gnd
Rt
CS Comp
OCSet
3V
20uA
20uA
64uA
Max
SS
LDO
0.8V
V
SEN33
/ SDB
Drv2
Drv3
Drv4
0.8V
VccLDO
Fb2
Fb3
Fb4
Bias
Generator
0.8V
3V
POR
VccLDO
UVLO
2.5V / 2.35V
1.27V / 1.2V
Vc
3.5V / 3.3V
Vcc
4.2V / 4.0V
Enbl
12
17
16
15
14
11
4
18
19
20
1
2
3
7
8
6
5
9
10
13
64uA
Max
64uA
Max
25K
25K
25K
25K
1.27V
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