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PDF IRU3055 Data sheet ( Hoja de datos )
| Número de pieza | IRU3055 | |
| Descripción | 5-BIT PROGRAMMABLE 3-PHASE SYNCHRONOUS BUCK CONTROLLER IC | |
| Fabricantes | International Rectifier | |
| Logotipo |  |
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Data Sheet No. PD94262
IRU3055
5-BIT PROGRAMMABLE 3-PHASE
SYNCHRONOUS BUCK CONTROLLER IC
PRELIMINARY DATA SHEET TEST SPEC
FEATURES
DESCRIPTION
Meets VRM 9.0 Specification
3-Phase Controller with On-Board MOSFET Driver
On-Board DAC programs the output voltage from
1.075V to 1.850V
Loss-less Short Circuit Protection
Programmable Frequency
Synchronous operation allows maximum efficiency
Minimum Part Count
Soft-Start
Power Good Function
Hiccup Mode Current Limit
APPLICATIONS
The IRU3055 is a 3-phase synchronous Buck controller
which provides high performance DC to DC converter for
high current applications.
The IRU3055 controller IC is specifically designed to meet
Intel and AMD specifications for the new microproces-
sor requiring low voltage and high current.
The IRU3055 features under-voltage lockout for both 5V
and 12V supplies, an external and programmable soft-
start function as well as programming the oscillator fre-
quency by using an external resistor.
Intel Pentium 4 and AMD K7
TYPICAL APPLICATION
C1
1uF
5V Vcc
C5
1uF
Ref
Rt
V CL1
V CL23
HDrv1
OCSet
LDrv1
PGnd1/
OCGnd
CS1
C9 R3
1uF 47K
SS
C10
0.1uF
D4
D3
D2
D1
HDrv2
IRU3055
LDrv2
PGnd2
CS2
HDrv3
C12 R6
22nF 27K
C7
100pF
(Optional)
D0
Comp
LDrv3
PGnd3
CS3
Fb
R1
2.2K
D1
C2
0.1uF
C3
1uF
L1
1uH
C4
1000uF
Q1
IRF3704S
Q2
IRF3711S
Q3
IRF3704S
Q4
IRF3711S
Q5
IRF3704S
Q6
IRF3711S
C6
6x 1500uF
L2
R2
1.5K
1uH
C8
1uF
L3
R4
1.5K
1uH
C11
1uF
L4
R5
1.5K
1uH
C13
1uF
Figure 1 - Typical application of IRU3055.
12V
1.5V / 60A
C14
8x 2700uF
PACKAGE ORDER INFORMATION
TA (8C)
0 To 70
DEVICE
IRU3055CQ
PACKAGE
36-Pin Plastic QSOP WB (Q)
Rev. 1.4
08/13/02
www.irf.com
1
1 page  
IRU3055
PIN#
15
16
17
28
18
19
20
21
31
22
30
32
23
27
34
24
26
35
25
36
29
33
PIN SYMBOL
Fault
OCSet
Gnd
SD
PGood
Ref
VCH3
VCH12
HDrv3
HDrv2
HDrv1
PGnd3
PGnd2
PGnd1
LDrv3
LDrv2
LDrv1
VCL23
VCL1
NC
OCGnd
PIN DESCRIPTION
Fault detector. When the output exceeds the OVP trip point, the fault pin switches to
2.8V and pulls down the soft-start.
This pin is connected to the drain of the synchronous MOSFET in channel 1 of the Core
supply and it provides the positive sensing for the internal current sensing circuitry. An
external resistor programs the over current threshold depending on the RDS(ON) of the
power MOSFET.
Analog ground for internal reference and control circuitry. Connect to PGnd with a short
trace.
Shut down pin. Pulling-up this pin disables the outputs.
Power good pin. This pin is a collector output that switches Low when the output of the
converter is not within 610%(typ) of the nominal output voltage.
2V reference output.
These pins power the high side MOSFET driver. A minmum 1mF ceramic cap must be
connected from these pins to ground to provide peak drive current capability.
Output drivers for the high side power MOSFET.
These pins serve as the ground pins and must be connected directly to the ground plane.
A high frequency capacitor (0.1 to 1mF) must be connected from pins VCL1, VCL23 and
VCH3, VCH12 to PGnd1, 2 and 3 for noise free operation.
Output driver for the synchronous power MOSFET.
These pins are connected to the 12V supply and serves as the power Vcc pin for the low
side output drivers. A high frequency capacitor (0.1 to 1mF) must be connected directly
from these pins to PGnd1, PGnd2 and PGnd3 pins in order to supply the peak current to
the power MOSFET during the transitions.
No connection.
This pin is connected from the source of the synchronous MOSFET in channal 1 of the
Core supply and it provides the reference point for the internal current sensing circuitry.
Rev. 1.4
08/13/02
www.irf.com
5
5 Page 
IRU3055
Synchronous-Rectifier Driver
VC1
VCH12
VCH3
C1 C2
C3
VIN
IRU3055
L1
Phase 1
Figure 11 - Supply VCH12, VCH3 with
charge bump configuration.
Synchronous rectification reduces conduction losses in
the rectifier by shunting the normal Schottky diode or
MOSFET body diode with a low on-resistance MOSFET
switch. The synchronous rectification also ensures good
transient dynamic. For IRU3055, the 3-phase synchro-
nous rectifier MOSFET drivers are built inside. To drive
the high-side MOSFET, it is necessary to supply a gate
voltage at least 4V greater than the bus voltage. In
IRU3055, the driver supply voltage for high side MOSFET
driver is supplied through the VCH12 and VCH3 pins. If the
input voltage for DC-DC converter is 5V, the VCH12 and
VCH3 pins can be connected to 12V or supplied by using
charge pump configuration as shown in Figure 11.
Component Selection Guide
Output Inductor Selection
The inductor is selected based on the inductor current
ripple, operation frequency and efficiency consideration.
In general, a large inductor results in small output ripple
and higher efficiency but big size. A small value inductor
causes large current ripple and poor efficiency but small
size. Generally, the inductor is selected based on the
output current ripple. The optimum point is usually found
between 20% and 50% ripple of output inductor current.
For each phase synchronous buck converter, the output
peak-to-peak current ripple is given by:
Di(PEAK - PEAK) = (VIN-VOUT)3VOUT/(L3Fs3VIN) ---(6)
Assuming the output current is evenly distributed in each
phase, we can define the ratio of the ripple current and
nominal output current as:
LIR = Di(PEAK - PEAK) / IOUT / m
Where LIR is typically between 20% to 50% and m is
the phase number. In this case m=3. Then the inductor
can be selected by:
L>VOUT3(VIN-VOUT)/(Fs3VIN3LIR3IOUT/m) ---(7)
For example, in the application circuit, the ripple is se-
lected as LIR=40%, the inductor is selected as:
L>1.53(12-1.5)/(150K312340%360A/3)=1.1mH
Select L=1mH
If the voltage Vc1 and VIN in Figure 11 is connected to
input voltage 12V, the voltage at VCH12 and VCH3 pins are
charged up to almost twice the input voltage. The high
side driver can be enabled. A capacitor in the range of
0.1mF to 1mF is generally adequate for capacitor C2.
For high current applications, a large ceramic capacitor
such as 2.2mF is recommended. The diode can be a
Schottky diode such as BAT54S.
With the charge bump configuration, shown in Figure
11, the voltage at pins VCH12 and VCH3 can be boosted
up. When the low side MOSFET is on, the capacitor C2
is charged to voltage Vc1. When the high side MOSFET
is ON, the energy in the capacitor C2 is discharged to
the bypass capacitor C1 next to pins VCH12 and VCH3.
The voltage at VCH12 and VCH3 pins is approximately the
sum of the voltage Vc1 and VIN. The high side driver
signal should be at least 4V higher than the input volt-
age (VIN). The voltage Vc1 has to be 5V or higher. For
the demo-board, Vc1 is equal to input voltage (VIN=12V).
If the low power dissipation of IC is preferred, especially
at higher frequency, Vc1 can be connected to 5V in-
stead.
The RMS current of the inductor will be approximately
equal to average current:
IOUT/m = 60/3 = 20A.
The peak inductor current is about:
IL(PEAK) = (1+LIR/2)3IOUT/m = 1.2320 = 24A
Output capacitor selection
The voltage rating of the output capacitor is the same as
output voltage. Typical available capacitors on the mar-
ket are electrolytic, tantalum and ceramic. If electrolytic
or tantalum capacitors are employed, the criteria is nor-
mally based on the value of Effective Series Resistance
(ESR) of total output capacitor. In most cases, the ESR
of the output capacitor is calculated based on the follow-
ing relationship:
ESR < DV/Di
---(8)
Where DV is the maximum allowed output voltage drop
during the transient and Di is the maximum output cur-
rent variation. In the worst case, Di is the maximum out-
put current minus zero.
Rev. 1.4
08/13/02
www.irf.com
11
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet IRU3055.PDF ] | |
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