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PDF IRU3004 Data sheet ( Hoja de datos )
| Número de pieza | IRU3004 | |
| Descripción | 5-BIT PROGRAMMABLE SYNCHRONOUS BUCK CONTROLLER IC | |
| Fabricantes | International Rectifier | |
| Logotipo |  |
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Data Sheet No. PD94140
IRU3004
5-BIT PROGRAMMABLE SYNCHRONOUS BUCK
CONTROLLER IC WITH DUAL LDO CONTROLLER
FEATURES
Meets latest VRM 8.4 specification for PentiumIII
Provides single chip solution for Vcore, GTL+ and
clock supply
On-Board DAC programs the output voltage from
1.3V to 3.5V. The IRU3004 remains on for VID code
of (11111)
Dual linear regulator controller on-board for 1.5V
GTL+ and 2.5V clock supplies
Loss-less Short Circuit Protection
Synchronous operation allows maximum efficiency
Patented architecture allows fixed frequency opera-
tion as well as 100% duty cycle during dynamic
load
Minimum Part Count, No External Compensation
Soft-Start Function
High current totem pole driver for direct driving of the
external power MOSFET
Power Good Function
APPLICATIONS
Pentium III & next generation processor DC to DC
converter application
Low Cost Pentium with AGP
DESCRIPTION
The IRU3004 controller IC is specifically designed to meet
Intel specifications for Pentium III™ microprocessor
applications as well as the next generation P6 family
processors. The IC provides a single chip controller IC
for the Vcore, GTL+ and clock supplies required for the
Pentium III applications. The IRU3004 features a pat-
ented topology, that in combination with a few external
components as shown in the typical application circuit,
will provide 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 meeting
the latest VRM specification. The IRU3004 also features
loss-less current sensing by using the RDS(on) of the high
side power MOSFET as the sensing resistor and a Power
Good window comparator that switches its open collec-
tor output low when the output is outside of a ±10%
window. Other features of the device are: under-voltage
lockout for both 5V and 12V supplies, an external pro-
grammable soft-start function as well as programming
the oscillator frequency by using an external capacitor.
TYPICAL APPLICATION
5V L1
Q1
C5 R1
C13 C3
R2
L2 Note: Pentium III is trademark of Intel Corp.
R16 R17
VOUT 3
C7 C16
Q2 C10
R4
R3
R12 R13
3.3V
C4
12V
R18
V12
C1
C2
Ct
SS
D4
VID4
VID3
VID2
VID1
VID0
C6 Q3
V5 CS+ HDrv CS- LDrv Gnd VFB3
IRU3004
Lin1
VFB1
D3 D2 D1 D0 VFB2 PGd Lin2
3.3V
R11
C15
Q4
C9
R5 R9
C8 Power Good
C14
Figure 1 - Typical application of the IRU3004.
VOUT 1
C11
R7
R8
VOUT 2
C12
R14
R15
PACKAGE ORDER INFORMATION
TA (8C)
0 To 70
0 To 70
DEVICE
IRU3004CW
IRU3004CF
PACKAGE
20-Pin Plastic SOIC (W)
20-Pin Plastic TSSOP (F)
Rev. 1.7
07/16/02
www.irf.com
1
1 page  
BLOCK DIAGRAM
IRU3004
V12 12
V5 5
D0 19
D1 18
D2 17
D3 16
D4 15
VFB2 4
Lin2 20
Enable
UVLO
Vset
Enable
5Bit
DAC,
Ctrl
Logic
Lin1 2
VFB1 3
Vset
+
Slope
Comp
Enable
PWM
Control
Osc
V12
V12
Soft
Start &
Fault
Logic
Enable
Over
Current
200uA
1.1Vset
14 VFB3
9 HDrv
11 LDrv
7 CS-
8 CS+
1 Ct
13 SS
6 PGd
1.5V
10 Gnd
0.9Vset
Figure 2 - Simplified block diagram of the IRU3004.
Rev. 1.7
07/16/02
www.irf.com
5
5 Page 
IRU3004
Output Inductor Selection
The output inductance must be selected such that un-
der low line and the maximum output voltage condition,
the inductor current slope times the output capacitor
ESR is ramping up faster than the capacitor voltage is
drooping during a load current step. However, if the in-
ductor is too small, the output ripple current and ripple
voltage become too large. One solution to bring the ripple
current down is to increase the switching frequency,
however that will be at the cost of reduced efficiency and
higher system cost. The following set of formulas are
derived to achieve the optimum performance without
many design iterations.
The maximum output inductance is calculated using the
following equation:
( )L = ESR3C3
VIN(MIN) - Vo(MAX)
2 3 ∆I
Where:
VIN(MIN) = Minimum input voltage
Vo = 2.8V , DI = 14.2A
( )L = 0.006390003
4.75 - 2.8
2314.2
= 3.7mH
Assuming that the programmed switching frequency is
set at 200KHz, an inductor is designed using the
Micrometals’ powder iron core material. The summary
of the design is outlined below:
The selected core material is Powder Iron, the selected
core is T50-52D from Micro Metal wound with 8 turns of
#16 AWG wire, resulting in 3mH inductance with ≈ 3mV
of DC resistance.
Assuming L=3mH and Fsw=200KHz (switching fre-
quency), the inductor ripple current and the output ripple
voltage is calculated using the following set of equations:
T ≡ Switching Period
D ≡ Duty Cycle
Vsw ≡ High side Mosfet ON Voltage
RDS ≡ Mosfet On Resistance
Vsync ≡ Synchronous MOSFET ON Voltage
DIr ≡ Inductor Ripple Current
DVo ≡ Output Ripple Voltage
T
=
1
Fsw
Vsw = Vsync = Io3RDS
Vo + Vsync
D ≈ VIN - Vsw + Vsync
TON = D3T
TOFF = T - TON
DIr = (Vo + Vsync)3 TOFF
L
DVo = DIr3ESR
In our example for Vo=2.8V and 14.2A load, assuming
IRL3103 MOSFET for both switches with maximum on-
resistance of 19mV, we have:
T
=
1
200000
=
5ms
Vsw = Vsync = 14.2 3 0.019 = 0.27V
D
≈
5
2.8 + 0.27
- 0.27 + 0.27
= 0.61
TON = 0.61 3 5 = 3.1ms
TOFF = 5 - 3.1 = 1.9ms
DIr = (2.8 + 0.27) 3 1.9 = 1.94A
3
DVo = 1.94 3 0.006 = 0.011V = 11mV
Power Component Selection
Assuming IRL3103 MOSFETs as power components,
we will calculate the maximum power dissipation as fol-
lows:
For high-side switch the maximum power dissipation
happens at maximum Vo and maximum duty cycle.
(2.8 + 0.27)
DMAX ≈ (4.75 - 0.27 + 0.27) = 0.65
PDH = DMAX 3 Io2 3 RDS(MAX)
PDH = 0.65 3 14.22 3 0.029 = 3.8W
RDS(MAX) = Maximum RDS(ON) of the MOSFET (1258C)
For synchronous MOSFET, maximum power dissipa-
tion happens at minimum Vo and minimum duty cycle.
DMIN
≈
(2 + 0.27)
(5.25 - 0.27 + 0.27)
= 0.43
PDS = (1 - DMIN) 3 Io2 3 RDS(MAX)
PDS = (1 - 0.43) 3 14.22 3 0.029 = 3.33W
Heat Sink Selection
Selection of the heat sink is based on the maximum
allowable junction temperature of the MOSFETS. Since
we previously selected the maximum RDS(on) at 1258C,
then we must keep the junction below this temperature.
Selecting TO-220 package gives uJC=1.88C/W (from the
venders’ data sheet) and assuming that the selected
heat sink is black anodized, the heat-sink-to-case ther-
mal resistance is uCS=0.058C/W, the maximum heat sink
temperature is then calculated as:
Ts = TJ - PD 3 (uJC + uCS)
Ts = 125 - 3.82 3 (1.8 + 0.05) = 1188C
Rev. 1.7
07/16/02
www.irf.com
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet IRU3004.PDF ] | |
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