Data Sheet No. PD94698
IRU3072
20-PIN SYNCHRONOUS PWM CONTROLLER/
3 LDO CONTROLLER
FEATURES
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
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.
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
TYPICAL APPLICATION
3.3V
Q1
V
SEN33
/ SDB
R1
C2
10uF
2.15K
R2
1K
Vcc
C1
1uF
+5V
Drv2
Fb2
VccLDO
V
OUT2
2.5V
C3
1uF
Q2
V
OUT3
1.8V
C4
10uF
R3
1.25K
R4
1K
Drv3
Fb3
Vc
D1
L1
U1
IRU3072
Drv4
Fb4
HDrv
OCSet
C5
1uF
C6
0.1uF
1uH
C7
2x 47uF,16V
V
IN
=12V
C8
10uF
Q3
V
OUT4
1.5V
C9
10uF
R5
866
V
R6
1K
Q4
IRF7460
R7
6.81K
Q5
IRF7460
L2
1uH
C10 220pF
R8
3.3K
C11
15nF
R9
46.4K
C13
0.1uF
V
OUT1
1.2V @ 8A
C12
3x 330uF, 40m
V
6TPB330M, Poscap
R10
499
V
Comp
Rt
SS1
LDrv
Fb1
PGnd
R11
1K
C14
33nF
SSLDO
Gnd
Figure 1 - Typical application of IRU3072.
PACKAGE ORDER INFORMATION
T
A
(°C)
0 To 70
Rev. 1.0
3/25/04
DEVICE
IRU3072CH
PACKAGE
20-Pin MLPQ 4x4 (H)
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1
IRU3072
ABSOLUTE MAXIMUM RATINGS
Vcc and VccLDO Supply Voltage ..............................
Vc Supply Voltage ....................................................
Storage Temperature Range ......................................
Operating Junction Temperature Range .....................
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.
25V
25V
-65°C To 150°C
0°C To 125°C
PACKAGE INFORMATION
20-PIN MLPQ 4x4 (H)
SS
LDO
u
JA
=468C/W
SS1
16
15
14
13
12
11
Fb4
Fb3
19
20
18
Fb2
17
Drv4
Drv3
Drv2
VccLDO
Vcc
1
2
3
4
5
6
7
8
9
10
Comp
Fb1
Rt
V
S E N 3 3
/SDB
OCSet
PGnd
Gnd
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, the typical specification value applies over Vcc=5V, Vc=12V, VccLDO=5V and
T
A
=25°C. the Min and Max limits apply to the temperature range from 0 to 70°C. Low duty cycle pulse testing is
used which keeps junction and case temperatures equal to the ambient temperature.
PARAMETER
SYM
Feedback Voltage
Feedback Voltage
V
FB
Fb Voltage Line Regulation
L
REG
UVLO
UVLO Threshold - Vcc
UVLO V
CC
UVLO Hysteresis - Vcc
UVLO Threshold - Vc
UVLO V
C
UVLO Hysteresis - Vc
UVLO Threshold - VccLDO
UVLO V
CCLDO
UVLO Hysteresis - VccLDO
UVLO Threshold - V
SEN33
UVLO V
SEN33
UVLO Hysteresis - V
SEN33
UVLO Threshold - Fb1, 2, 3, 4 UVLO Fb1
UVLO Hysteresis - Fb1, 2, 3, 4
Supply Current
Vcc Dynamic Supply Current
Dyn I
CC
Vc Dynamic Supply Current
Dyn I
C
Vcc Static Supply Current
I
CCQ
Vc Static Supply Current
I
CQ
TEST CONDITION
MIN
0.784
5<Vcc<12
Supply Ramping Up
Supply Ramping Up
Supply Ramping Up
Supply Ramping Up
Fb Ramping Down
3.8
3.2
2.25
1.17
0.3
TYP
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
MAX
0.816
0.625
4.6
3.8
2.75
1.37
0.5
UNITS
V
%
V
V
V
V
V
V
V
V
V
V
mA
mA
mA
mA
Rev. 1.0
3/25/04
HDrv
LDrv
Vc
Freq=200KHz, C
L
=3000pF
Freq=200KHz, C
L
=3000pF
SS=0V
SS=0V
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14
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5
2
IRU3072
PARAMETER
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
SYM
TEST CONDITION
MIN
15
TYP
25
0.1
35
500
170
340
900
200
400
1.27
50
50
50
20
85
115
50
92
0
60
0.8
0.5
150
30
0
MAX
35
1
75
1300
230
460
UNITS
mA
mA
mA
mmho
KHz
V
PP
100
100
150
100
99
ns
ns
ns
ns
%
%
mA
V
mA
8C
mA
mV
SS I
B1
,I
B2
SS1=SS2=0V
I
FB1
I
FB2
SS1=3V
SS1=0V
Freq
V
RAMP
Tr
Tf
T
DB
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
D
MAX
Max Duty Cycle
D
MIN
Min Duty Cycle
LDO Controller Section
Drive Current
Drv2, 3 and 4
Fb Voltage
Input Bias Current
Thermal Shutdown
Note 1
Current Limit
I
OCSET
OC Threshold Set Current
V
OC(OFFSET)
OC Comp Off-Set Voltage
Note 1:
Guaranteed by design but not tested in production.
40
0.784
0.816
2
23
-7
37
+7
PIN DESCRIPTIONS
PIN#
1
2
3
4
5
PIN SYMBOL
PIN DESCRIPTION
Drv4
Outputs of the linear regulator controllers.
Drv3
Drv2
VccLDO
This pin provides power for the LDO controllers.
Vcc
This pin provides biasing for the internal blocks of the IC as well as power for the low side
driver. A minimum of 1mF, high frequency capacitor must be connected from this pin to
ground to provide peak drive current capability.
LDrv
Output driver for the synchronous power MOSFET.
Gnd
This pin serves as the ground pin and must be connected directly to the ground plane. A
high frequency capacitor (0.1 to 1mF) must be connected from Vcc, Vc and VccLDO pins
to this pin for noise free operation.
PGnd
This pin serves as the separate ground for MOSFET's driver and should be connected to
system's ground plane.
HDrv
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.
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7
8
9
Rev. 1.0
3/25/04
3
IRU3072
PIN#
10
PIN SYMBOL
PIN DESCRIPTION
Vc
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 1mF, high frequency capacitor must be connected from this pin to ground to
provide peak drive current capability.
OCSet
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.
V
SEN33
/SDB
This pin is used to monitor the 3.3V rail. This pin can be pulled-low to shutdown the
outputs.
Rt
This pin sets the switching frequency with a resistor to Gnd.
Fb1
This pin is connected directly to the output of the switching regulator via resistor divider to
provide feedback to the Error amplifier.
Comp
Compensation pin of the error amplifier. An external resistor and capacitor network is
typically connected from this pin to ground to provide loop compensation.
SS1
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.
SS
LDO
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.
Fb2
These pins provide feedback for the linear regulator controllers.
Fb3
Fb4
11
12
13
14
15
16
17
18
19
20
4
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Rev. 1.0
3/25/04
IRU3072
BLOCK DIAGRAM
V
SEN33
/ SDB
12
Bias
Generator
20uA
64uA
Max
64uA
Max
64uA
Max
Vcc
1.27V / 1.2V
4.2V / 4.0V
3.5V / 3.3V
2.5V / 2.35V
3V
1.27V
0.8V
POR
UVLO
SS
LDO
3V
17
Vc
20uA
64uA
Max
VccLDO
13
10
Rt
Oscillator
9
Rt
Vc
HDrv
SS1
POR
16
Ct
Enbl
S
Q
R
Reset Dom
5
Comp
0.8V
Fb1
3V
OCSet
15
25K
Error Amp
Error Comp
Vcc
25K
14
0.4V
20uA
8
CS Comp
11
64uA
3
25K=1.6V
When SS=0
POR
FbLo Comp
7
6
LDrv
PGnd
Gnd
VccLDO
4
0.8V
3
25K
Drv2
Fb2
18
2
25K
Drv3
Fb3
19
1
Fb4
25K
20
Drv4
Figure 2 - Simplified block diagram of the IRU3072.
Rev. 1.0
3/25/04
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