参数资料
| 型号： | ISL62881HRTZ |
| 厂商： | Intersil |
| 文件页数： | 20/35页 |
| 文件大小： | 0K |
| 描述： | IC REG PWM SGL PHASE 28TQFN |
| 标准包装： | 75 |
| 应用： | 控制器，Intel IMVP-6.5? |
| 输入电压： | 5 V ~ 25 V |
| 输出数： | 1 |
| 输出电压： | 0.013 V ~ 1.5 V |
| 工作温度： | -10°C ~ 100°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-WFQFN 裸露焊盘 |
| 供应商设备封装： | 28-TQFN-EP（4x4） |
| 包装： | 管件 |
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ISL62881, ISL62881B
V Cn ( s ) = R sen × I o ( s ) × A Rsen ( s )
1
A Rsen ( s ) = ----------------------
1 + ------------
ω Rsen = ---------------------------
R ntcnet
?
?
V Cn = ? ----------------------------------------- × DCR ? × I o
I droop = ----- × ----------------------------------------- × DCR × I o
Figure 18 shows two optional circuits for reduction of the ring
back. R ip and C ip form an R-C branch in parallel with R i , providing
a lower impedance path than R i at the beginning of i o change.
R ip and C ip do not have any effect at steady state. Through
proper selection of R ip and C ip values, i droop can resemble i o
rather than i L , and V o will not ring back. The recommended value
for R ip is 100W. C ip should be determined through tuning the
load transient response waveforms on an actual board. The
recommended range for C ip is 100pF~2000pF.
C n is the capacitor used to match the inductor time constant. It
usually takes the parallel of two (or more) capacitors to get the
desired value. Figure 18 shows that two capacitors C n.1 and C n.2
are in parallel. Resistor R n is an optional component to reduce
the V o ring back. At steady state, C n.1 + C n.2 provides the desired
C n capacitance. At the beginning of i o change, the effective
capacitance is less because R n increases the impedance of the
C n.1 branch. As Figure 15 explains, V o tends to dip when C n is too
small, and this effect will reduce the V o ring back. This effect is
more pronounced when C n.1 is much larger than C n.2 . It is also
more pronounced when R n is bigger. However, the presence of
R n increases the ripple of the V n signal if C n.2 is too small. It is
recommended to keep C n.2 greater than 2200pF. R n value
usually is a few ohms. C n.1 , C n.2 and R n values should be
determined through tuning the load transient response
waveforms on an actual board.
R ip and C ip form an R-C branch in parallel with R i , providing a
lower impedance path than R i at the beginning of i o change. R ip
and C ip do not have any effect at steady state. Through proper
selection of R ip and C ip values, i droop can resemble i o rather than
i L , and V o will not ring back. The recommended value for R ip is
100 Ω . C ip should be determined through tuning the load
transient response waveforms on an actual board. The
recommended range for C ip is 100pF~2000pF. However, it
should be noted that the R ip -C ip branch may distort the i droop
waveform. Instead of being triangular as the real inductor
current, i droop may have sharp spikes, which may adversely
affect i droop average value detection and therefore may affect
OCP accuracy. User discretion is advised.
Resistor Current-Sensing Network
Figure 19 shows the resistor current-sensing network. The
inductor has a series current-sensing resistor R sen . R sum and is
connected to the R sen pad to accurately capture the inductor
current information. The R sum feeds the sensed information to
capacitor C n . R sum and C n form a a filter for noise attenuation.
Equations 13 through 15 gives V Cn (s) expressions:
(EQ. 13)
(EQ. 14)
s
ω sns
1 (EQ. 15)
R sum × C n
Transfer function A Rsen (s) always has unity gain at DC.
Current-sensing resistor R sen value will not have significant
variation over-temperature, so there is no need for the NTC
network.
The recommended values are R sum = 1k Ω and C n = 5600pF.
Overcurrent Protection
Referring to Equation 1 and Figures 12, 13 and 19, resistor R i
sets the droop current I droop . Table 3 shows the internal OCP
threshold. It is recommended to design I droop without using the
R comp resistor.
For example, the OCP threshold is 20μA. We will design I droop to
be 14μA at full load, so the OCP trip level is 1.43x of the full load
current.
For inductor DCR sensing, Equation 16 gives the DC relationship
of V cn (s) and I o (s).
(EQ. 16)
? R ntcnet + R sum ?
Substitution of Equation 16 into Equation 1 gives:
2 R ntcnet (EQ. 17)
R i R ntcnet + R sum
PHASE
Therefore:
( R ntcnet + R sum ) × I droop
L
2R ntcnet × DCR × I o
R i = ---------------------------------------------------------------------
(EQ. 18)
Substitution of Equation 8 and application of the OCP condition
DCR
in Equation 18 gives:
2 × --------------------------------------------------- × DCR × I omax
? ( R ntcs + R ntc ) × R p
R i = ---------------------------------------------------------------------------------------------------------------
? --------------------------------------------------- + R sum ? × I droopmax
RSEN
RSUM
Vcn
Cn
Ri
ISUM+
ISUM-
( R ntcs + R ntc ) × R p
R ntcs + R ntc + R p
? R ntcs + R ntc + R p ?
?
(EQ. 19)
Io
FIGURE 19. RESISTOR CURRENT-SENSING NETWORK
20
where I omax is the full load current, I droopmax is the corresponding
droop current. For example, given R sum = 3.65k Ω , R p = 11k Ω , R ntcs
= 2.61k Ω , R ntc = 10k Ω , DCR = 1.1m Ω , I omax = 14A and
I droopmax = 14μA, Equation 19 gives R i = 1.36k Ω .
For resistor sensing, Equation 20 gives the DC relationship of
V cn (s) and I o (s).
FN6924.3
June 16, 2011
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| ISL62881HRTZ-T | 功能描述:直流/直流开关调节器 1 PHS PWM BUCKG FOR MICROPROCESR PWR SUP RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
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| ISL62882BHRTZ | 功能描述:直流/直流开关调节器 2 PHS PWM BUCKG FOR MICROPROC PWR SUP RoHS:否 制造商:International Rectifier 最大输入电压:21 V 开关频率:1.5 MHz 输出电压:0.5 V to 0.86 V 输出电流:4 A 输出端数量: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:PQFN 4 x 5 |
| ISL62882BHRTZR5411 | 制造商:Intersil Corporation 功能描述: |
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