参数资料
| 型号： | ISL6308CRZ |
| 厂商： | Intersil |
| 文件页数： | 13/28页 |
| 文件大小： | 0K |
| 描述： | IC CTRLR PWM 3PHASE BUCK 40-QFN |
| 标准包装： | 500 |
| 应用： | 控制器，DDR |
| 输入电压： | 5 V ~ 12 V |
| 输出数： | 1 |
| 输出电压： | 0.6 V ~ 2.3 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 40-VFQFN 裸露焊盘 |
| 供应商设备封装： | 40-QFN（6x6） |
| 包装： | 管件 |
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ISL6308
Load Line (Droop) Regulation
DCR
In some high current applications, a requirement on a
precisely controlled output impedance is imposed. This
dependence of output voltage on load current is often
termed “droop” or “load line” regulation.
The Droop is an optional feature in the ISL6308. It can be
PHASE1
R S
I
V L (s)
L1
INDUCTOR
L 1
I OUT
V OUT
C OUT
enabled by connecting ICOMP pin to DROOP pin, as shown
L2
DCR
in Figure 6. To disable it, connect the DROOP pin to IREF
pin.
As shown in Figure 6, a voltage, V DROOP , proportional to the
total current in all active channels, I OUT , feeds into the
PHASE2
ISUM
R S
I
INDUCTOR
L 2
differential remote-sense amplifier. The resulting voltage at
the output of the remote-sense amplifier is the sum of the
output voltage and the droop voltage. As Equation 4 shows,
feeding this voltage into the compensation network causes
the regulator to adjust the output voltage so that it’s equal to
-
ICOMP
C COMP
R COMP
the reference voltage minus the droop voltage.
DROOP
The droop voltage, V DROOP , is created by sensing the
current through the output inductors. This is accomplished
V DROOP
+
IREF
C SUM
(Optional)
by using a continuous DCR current sensing method.
Inductor windings have a characteristic distributed
resistance or DCR (Direct Current Resistance). For
simplicity, the inductor DCR is considered as a separate
lumped quantity, as shown in Figure 7. The channel current,
I L , flowing through the inductor, passes through the DCR.
Equation 6 shows the S-domain equivalent voltage, V L ,
across the inductor.
ISL6308
FIGURE 7. DCR SENSING CONFIGURATION
By simply adjusting the value of R S , the load line can be set
to any level, giving the converter the right amount of droop at
all load currents. It may also be necessary to compensate for
V L ( s ) = I L ? ( s ? L + DCR )
(EQ. 6)
any changes in DCR due to temperature. These changes
cause the load line to be skewed, and cause the R-C time
The inductor DCR is important because the voltage dropped
across it is proportional to the channel current. By using a
simple R-C network and a current sense amplifier, as shown
in Figure 7, the voltage drop across all of the inductors DCRs
can be extracted. The output of the current sense amplifier,
V DROOP , can be shown to be proportional to the channel
currents I L1 , I L2 , and I L3 , shown in Equation 7.
constant to not match the L/DCR time constant. If this
becomes a problem a simple negative temperature
coefficient resistor network can be used in the place of
R COMP to compensate for the rise in DCR due to
temperature.
Output Voltage Offset Programming
The ISL6308 allows the designer to accurately adjust the
? ------------- + 1 ?
s ? L
? DCR ? R COMP
( s ? R ? C + 1 ) R
VDROOP ( s ) = -------------------------------------------------------------------------- ? ----------------------- ? ( I
COMP COMP S
L1 + I L2 + I L3 ) ? DCR
(EQ. 7)
offset voltage by connecting a resistor, R OFS , from the OFS
pin to VCC or GND. When R OFS is connected between OFS
and VCC, the voltage across it is regulated to 1.5V. This
causes a proportional current (I OFS ) to flow into the OFS pin
If the R-C network components are selected such that the
R-C time constant matches the inductor L/DCR time
constant, then V DROOP is equal to the sum of the voltage
drops across the individual DCRs, multiplied by a gain. As
Equation 8 shows, V DROOP is therefore proportional to the
total output current, I OUT .
and out of the FB pin. If R OFS is connected to ground, the
voltage across it is regulated to 0.5V, and I OFS flows into the
FB pin and out of the OFS pin. The offset current flowing
through the resistor between VDIFF and FB will generate
the desired offset voltage which is equal to the product
(I OFS x R 1 ). These functions are shown in Figures 8 and 9.
V DROOP = --------------------- ? I OUT ? DCR
R COMP
R S
13
(EQ. 8)
FN9208.4
September 30, 2008
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| ISL6308CRZR5374 | 制造商:Intersil Corporation 功能描述:ISL6308CRZ W/ 24HR BURN-IN - Rail/Tube 制造商:Intersil Corporation 功能描述:IC CTRLR PWM 3PHASE BUCK 40-QFN 制造商:Intersil 功能描述:ISL6308CRZ W/24HRU RN-IN |
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