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IRU3038 の電気的特性と機能

IRU3038のメーカーはInternational Rectifierです、この部品の機能は「SYNCHRONOUS PWM CONTROLLER FOR TERMINATION POWER SUPPLY APPLICATIONS」です。


製品の詳細 ( Datasheet PDF )

部品番号 IRU3038
部品説明 SYNCHRONOUS PWM CONTROLLER FOR TERMINATION POWER SUPPLY APPLICATIONS
メーカ International Rectifier
ロゴ International Rectifier ロゴ 




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IRU3038 Datasheet, IRU3038 PDF,ピン配置, 機能
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Data Sheet No. PD94250
IRU3038
SYNCHRONOUS PWM CONTROLLER
FOR TERMINATION POWER SUPPLY APPLICATIONS
PRELIMINARY DATA SHEET
FEATURES
DESCRIPTION
Synchronous Controller in 14-Pin Package
Operating with single 5V or 12V supply voltage
200KHz to 400KHz operation set by an external
resistor
Soft-Start Function
Fixed Frequency Voltage Mode
500mA Peak Output Drive Capability
Uncommitted Error Amplifier available for DDR
voltage tracking application
1.25V Reference Voltage
Protects the output when control FET is shorted
APPLICATIONS
DDR memory source sink Vtt application
Low cost on-board DC to DC such as
5V to 3.3V, 2.5V or 1.8V
Graphic Card
Hard Disk Drive
The IRU3038 controller IC is designed to provide a low
cost synchronous Buck regulator for voltage tracking
applications such DDR memory and general purpose
on-board DC to DC converter. Modern micro processors
combined with DDR memory, need high-speed bandwidth
data bus which requires a particular bus termination volt-
age. This voltage will be tightly regulated to track the
half of chipset voltage for best performance. The IRU3038
together with dual N-channel MOSFETs such as IRF7313,
provide a low cost solution for such applications. This
device features a programmable frequency set from
200KHz to 400KHz, under-voltage lockout for both Vcc
and Vc supplies, an external programmable soft-start
function as well as output under-voltage detection that
latches off the device when an output short is detected.
TYPICAL APPLICATION
VDDQ
(2.5V)
DDR
Memory
C1
0.1uF
R1
1K
R2
1K C5
0.1uF
C7
2200pF
R3
33K
Vcc
VREF
Vc
HDrv
VP
SS U1
IRU3038
LDrv
Rt
Comp
PGnd
Fb
Gnd
12V
C2
1uF
C3
10TPB100M,
100uF, 55mV
L1
1uH
D1
BAT54
or 1N4148
Q1
1/2 of IRF7313
L2
D03316P-103, 10uH, 3.9A
Q2
1/2 of IRF7313
5V
C4
47uF
Vtt
1.25V @ 3A
C6
2x 6TPB150M,
150uF, 55mV
Figure 1 - Typical application of IRU3038 when Vtt tracks the VDDQ.
PACKAGE ORDER INFORMATION
TA (°C)
0 To 70
0 To 70
DEVICE
IRU3038CF
IRU3038CS
PACKAGE
14-Pin Plastic TSSOP (F)
14-Pin Plastic SOIC NB (S)
Rev. 2.0
09/12/02
www.irf.com
www.DataSheet4U.com
1

1 Page





IRU3038 pdf, ピン配列
IRU3038
PARAMETER
Error Amp
Fb Voltage Input Bias Current
Fb Voltage Input Bias Current
VP Voltage Range
Transconductance
Oscillator
Frequency
Ramp Amplitude
Output Drivers
Rise Time
Fall Time
Dead Band Time
Max Duty Cycle
Min Duty Cycle
SYM
TEST CONDITION
IFB1 SS=3V, Fb=1V
IFB2 SS=0V, Fb=1V
gm
Freq
V RAMP
Rt=Open
Rt=Gnd
Tr CLOAD=1500pF
Tf CLOAD=1500pF
TDB
TON Fb=1V, Freq=200KHz
TOFF Fb=1.5V
MIN
0.8
450
180
360
1.225
50
85
0
TYP
-0.1
-64
600
200
400
1.25
50
50
150
90
0
MAX UNITS
mA
mA
1.5 V
750 mmho
220
440
1.275
KHz
V
100 ns
100 ns
250 ns
95 %
%
PIN DESCRIPTIONS
PIN#
1
2
3
4
5
14
6
7
8
9
10
11
12
13
PIN SYMBOL
Fb
VP
VREF
Vcc
NC
PIN DESCRIPTION
This pin is connected directly to the output of the switching regulator via resistor divider to
provide feedback to the Error amplifier.
Non-inverting input of error amplifier.
Reference Voltage.
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.
No Connection.
LDrv
Gnd
PGnd
HDrv
Vc
Rt
Comp
SS
Output driver for the synchronous power MOSFET.
Analog ground for internal reference and control circuitry. Connect to PGnd with a short
trace.
This pin serves as the separate ground for MOSFET's drivers and should be connected to
system's ground plane. A high frequency capacitor (0.1 to 1mF) must be connected from
Vcc and Vc pins to this pin for noise free operation.
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.
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.
The switching frequency can be Programmed between 200KHz and 400KHz by connect-
ing a resistor between Rt and Gnd. Floating the pin set the switching frequency to 200KHz
and grounding the pin set the switching frequency to 400KHz.
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. The converter can be shutdown by pulling this pin below 0.5V.
Rev. 2.0
09/12/02
www.irf.com
3


3Pages


IRU3038 電子部品, 半導体
IRU3038
Output Capacitor Selection
The criteria to select the output capacitor is normally
based on the value of the Effective Series Resistance
(ESR). In general, the output capacitor must have low
enough ESR to meet output ripple and load transient
requirements, yet have high enough ESR to satisfy sta-
bility requirements. The ESR of the output capacitor is
calculated by the following relationship:
ESR
[
DVO
DIO
---(4)
Where:
DVO = Output Voltage Ripple
DIO = Output Current
DVO=100mV and DIO=4A
This results to: ESR=25mV
If Di = 30%(IO), then the output inductor will be:
L = 2.6mH
The Coilcraft DO5022HC series provides a range of in-
ductors in different values, low profile suitable for large
currents, 3.3mH, 10A is a good choice for this applica-
tion. This will result to a ripple approximately 26.5% of
output current.
Power MOSFET Selection
The IRU3038 uses two N-Channel MOSFETs. The se-
lections criteria to meet power transfer requirements is
based on maximum drain-source voltage (VDSS), gate-
source drive voltage (VGS), maximum output current, On-
resistance RDS(ON) and thermal management.
The Sanyo TPC series, Poscap capacitor is a good choice.
The 6TPC150M 150mF, 6.3V has an ESR 40mV. Se-
lecting two of these capacitors in parallel, results to an
ESR of 20mV which achieves our low ESR goal.
The capacitor value must be high enough to absorb the
inductor's ripple current. The larger the value of capaci-
tor, the lower will be the output ripple voltage.
The MOSFET must have a maximum operating voltage
(VDSS) exceeding the maximum input voltage (VIN).
The gate drive requirement is almost the same for both
MOSFETs. Logic-level transistor can be used and cau-
tion should be taken with devices at very low VGS to pre-
vent undesired turn-on of the complementary MOSFET,
which results a shoot-through current.
Inductor Selection
The inductor is selected based on output power, operat-
ing frequency and efficiency requirements. Low inductor
value causes large ripple current, resulting in the smaller
size, but poor efficiency and high output noise. Gener-
ally, the selection of inductor value can be reduced to
desired maximum ripple current in the inductor (i). The
optimum point is usually found between 20% and 50%
ripple of the output current.
For the buck converter, the inductor value for desired
operating ripple current can be determined using the fol-
lowing relation:
VIN
-
VOUT
=
L3
Di
Dt
;
Dt
=
D3
1
fS
;
D
=
VOUT
VIN
L
=
(V IN
-
VOUT)3
VOUT
VIN3Di3fS
---(5)
Where:
VIN = Maximum Input Voltage
VOUT = Output Voltage
i = Inductor Ripple Current
fS = Switching Frequency
t = Turn On Time
D = Duty Cycle
The total power dissipation for MOSFETs includes con-
duction and switching losses. For the Buck converter,
the average inductor current is equal to the DC load cur-
rent. The conduction loss is defined as:
PCOND (Upper Switch) = IL2OAD 3 RDS(ON) 3 D 3 q
PCOND (Lower Switch) = IL2OAD 3 RDS(ON) 3 (1 - D) 3 q
q = RDS(ON) Temperature Dependency
The RDS(ON) temperature dependency should be consid-
ered for the worst case operation. This is typically given
in the MOSFET data sheet. Ensure that the conduction
losses and switching losses do not exceed the package
ratings or violate the overall thermal budget.
Choose IRF7460 for both control MOSFET and synchro-
nous MOSFET. This device provides low on-resistance
in a compact SOIC 8-Pin package.
6 www.irf.com
Rev. 2.0
09/12/02

6 Page



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