IR3086AMPBF 데이터 시트보기 (PDF) - International Rectifier
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IR3086AMPBF Datasheet PDF : 33 Pages
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IR3086APbF
DESIGN EXAMPLE 1 - VRM 10 2U CONVERTER
SPECIFICATIONS
Input Voltage: VI=12 V
DAC Voltage: VDAC=1.35 V
No Load Output Voltage Offset: VO_NLOFST=20 mV
Output Current: IO=105 ADC
Maximum Output Current: IOMAX=120 ADC
Output Impedance: RO=0.91 mΩ
VCC Ready to VCC Power Good Delay: tVccPG=0-10mS
Soft Start Time: tSS=2 mS
Over Current Delay: tOCDEL< 0.5mS
Dynamic VID Down-Slope Slew Rate: SRDOWN=2.5mV/uS
Over Temperature Threshold: TPCB=115 ºC
POWER STAGE
Phase Number: n=6
Switching Frequency: fSW=400 kHz
Output Inductors: L=220 nH, RL=0.47 mΩ
Output Capacitors: AL-Polymer, C=560uF, RC= 7mΩ, Number Cn=10
IR3081A EXTERNAL COMPONENTS
Oscillator Resistor Rosc
Once the switching frequency is chosen, ROSC can be determined from the curve in Figure 13 of IR3081A Data
Sheet. For switching frequency of 400kHz per phase, choose ROSC=30.1kΩ
Soft Start Capacitor CSS/DEL and Resistor RSS/DEL
Determine the soft start capacitor from the required soft start time.
C SS / DEL
= I CHG ∗ t SS
VO
=
70 *10−6 ∗ 2 *10−3
1.35 − 20 *10−3
= 0.1uF
The soft start delay time is
tSSDEL
=
CSS
/ DEL ∗1.3
ICHG
=
0.1*10−6 ∗1.3
70 *10−6
= 1.86mS
The power good delay time is
tVccPG
=
CSS
/ DEL
* (3.735 −VO
ICHG
− 1.3)
=
0.1*10−6
* (3.735 −1.33 −1.3)
70 *10−6
=
1.58ms
Over current delay time is
tOCDEL
=
CSS / DEL * 0.115
IOCDISCHG
=
0.1*10−6 * 0.115
40 *10−6
=
0.29ms
Page 21 of 33
9/30/04
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