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PDF IRU3037APBF Data sheet ( Hoja de datos )
| Número de pieza | IRU3037APBF | |
| Descripción | 8-PIN SYNCHRONOUS PWM CONTROLLER | |
| Fabricantes | International Rectifier | |
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Data Sheet No. PD94173 revD
IRU3037/IRU3037A & (PbF)
8-PIN SYNCHRONOUS PWM CONTROLLER
FEATURES
Synchronous Controller in 8-Pin Package
Operating with single 5V or 12V supply voltage
Internal 200KHz Oscillator
(400KHz for IRU3037A)
Soft-Start Function
Fixed Frequency Voltage Mode
500mA Peak Output Drive Capability
Protects the output when control FET is shorted
SOIC 8-Lead also available LEAD-FREE
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
DESCRIPTION
The IRU3037 controller IC is designed to provide a low
cost synchronous Buck regulator for on-board DC to DC
converter applications. With the migration of today’s ASIC
products requiring low supply voltages such as 1.8V and
lower, together with currents in excess of 3A, traditional
linear regulators are simply too lossy to be used when
input supply is 5V or even in some cases with 3.3V
input supply. The IRU3037 together with dual N-channel
MOSFETs such as IRF7313, provide a low cost solution
for such applications. This device features an internal
200KHz oscillator (400KHz for "A" version), under-volt-
age lockout for both Vcc and Vc supplies, an external
programmable soft-start function as well as output un-
der-voltage detection that latches off the device when an
output short is detected.
TYPICAL APPLICATION
12V
C3 C4
1uF 1uF
C2
10TPB100M,
100uF, 55mΩ
L1
1uH
5V
C1
47uF
C8
0.1uF
C9
2200pF
R4
24k
Vcc Vc
HDrv
SS/SD U1
IRU3037
LDrv
Comp
Gnd
Fb
Q1
1/2 of IRF7313
L2
D05022P-562, 5.6uH, 5.3A
Q2
1/2 of IRF7313
R5
1.24K, 1%
R3
249, 1%
1.5V/5A
C7
2x 6TPC150M,
150uF, 40mΩ
Figure 1 - Typical application of IRU3037 or IRU3037A.
PACKAGE ORDER INFORMATION
TA (°C)
0 To 70
0 To 70
0 To 70
0 To 70
DEVICE LEADFREE DEVICE
IRU3037CF IRU3037CFPbF
IRU3037CS IRU3037CSPbF
IRU3037ACF IRU3037ACFPbF
IRU3037ACS IRU3037ACSPbF
PACKAGE
8-Pin Plastic TSSOP (F)
8-Pin Plastic SOIC NB (S)
8-Pin Plastic TSSOP (F)
8-Pin Plastic SOIC NB (S)
FREQUENCY
200KHz
200KHz
400KHz
400KHz
www.irf.com
1
1 page  
IRU3037/IRU3037A & (PbF)
APPLICATION INFORMATION
Design Example:
The following example is a typical application for IRU3037,
the schematic is Figure 18 on page 14.
VIN = 5V
VOUT = 3.3V
IOUT = 4A
∆VOUT = 100mV
fS = 200KHz
Soft-Start Programming
The soft-start timing can be programmed by selecting
the soft start capacitance value. The start up time of the
converter can be calculated by using:
tSTART = 75×Css (ms)
---(2)
Where:
CSS is the soft-start capacitor (µF)
Output Voltage Programming
Output voltage is programmed by reference voltage and
external voltage divider. The Fb pin is the inverting input
of the error amplifier, which is internally referenced to
1.25V (0.8V for IRU3037A). The divider is ratioed to pro-
vide 1.25V at the Fb pin when the output is at its desired
value. The output voltage is defined by using the follow-
ing equation:
( )VOUT = VREF ×
1 + R6
R5
---(1)
When an external resistor divider is connected to the
output as shown in Figure 3.
IRU3037
Fb
VOUT
R6
R5
Figure 3 - Typical application of the IRU3037 for
programming the output voltage.
Equation (1) can be rewritten as:
( )R6 = R5 ×
VOUT
VREF
-1
Choose R5 = 1KΩ
This will result to R6 = 1.65KΩ
If the high value feedback resistors are used, the input
bias current of the Fb pin could cause a slight increase
in output voltage. The output voltage set point can be
more accurate by using precision resistor.
For a start-up time of 7.5ms, the soft-start capacitor will
be 0.1µF. Choose a ceramic capacitor at 0.1µF.
Shutdown
The converter can be shutdown by pulling the soft-start
pin below 0.5V. The control MOSFET turns off and the
synchronous MOSFET turns on during shutdown.
Boost Supply Vc
To drive the high-side switch it is necessary to supply a
gate voltage at least 4V greater than the bus voltage.
This is achieved by using a charge pump configuration
as shown in Figure 18. The capacitor is charged up to
approximately twice the bus voltage. A capacitor in the
range of 0.1µF to 1µF is generally adequate for most
applications. In application, when a separate voltage
source is available the boost circuit can be avoided as
shown in Figure 1.
Input Capacitor Selection
The input filter capacitor should be based on how much
ripple the supply can tolerate on the DC input line. The
larger capacitor, the less ripple expected but consider
should be taken for the higher surge current during the
power-up. The IRU3037 provides the soft-start function
which controls and limits the current surge. The value of
the input capacitor can be calculated by the following
formula:
CIN
=
IIN × ∆t
∆V
---(3)
Where:
CIN is the input capacitance (µF)
IIN is the input current (A)
∆t is the turn on time of the high-side switch (µs)
∆V is the allowable peak to peak voltage ripple (V)
www.irf.com
5
5 Page 
IRU3037/IRU3037A & (PbF)
TYPICAL PERFORMANCE CHARACTERISTICS
IR U 3037A
V cc vs.Icc
@ 470P F ,1150P F and 1540P F G ate Load
TA = 25)C
14
12
CLOAD=1540pF
10
8 CLOAD=1150pF
6
4 CLOAD=470pF
2
0
0 2 4 6 8 10 12 14
V cc (V )
Figure 9 - Vcc vs. Icc
IRU3037A
Vc vs. Ic
@470PF, 1150PF and 1540PF Gate Load
TA = 25)C
30
25
CLOAD=1540pF
20
CLOAD=1150pF
15
10 CLOAD=470pF
5
0
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Vc (V)
Figure 10 - Vc vs. Ic
www.irf.com
11
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet IRU3037APBF.PDF ] | |
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