参数资料
型号: MAX1897ETP+T
厂商: Maxim Integrated Products
文件页数: 22/33页
文件大小: 0K
描述: IC REG CTRLR BUCK PWM 20-TQFN
标准包装: 2,500
系列: Quick-PWM™
PWM 型: 控制器
输出数: 1
频率 - 最大: 550kHz
电源电压: 4.5 V ~ 5.5 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: 0°C ~ 85°C
封装/外壳: 20-WQFN 裸露焊盘
包装: 带卷 (TR)
Quick-PWM Slave Controllers for
Multiphase, Step-Down Supplies
SLAVE CURRENT-LIMIT VOLTAGES
vs. AVERAGE INDUCTOR CURRENT
160
I ADJ(MIN) = I PEAK = ITHS
140
V ITHM(HIGH)
V
R CM
120
MASTER
100
80
V ITHM(LOW)
CONTROLLER
60
40
R CM I LM(PEAK) = R CS I LS(PEAK)
R CM I LM(VALLEY) = R CS I LS(VALLEY)
V ITHS
SLAVE
CONTROLLER
]
20
0
? I ADJ - ? I INDUCTOR =
[
V OUT (V IN - V OUT )
V IN f SW L
0
10
20
30
40
50
AVERAGE INDUCTOR CURRENT (A)
MASTER CURRENT-LIMIT VOLTAGES
vs. AVERAGE INDUCTOR CURRENT
160
( )
140
120
100
80
60
40
20
0
UNADJUSTED ? I LIMIT ≤ ? I LIMIT = V ITHM(HIGH)
V ITHM(HIGH)
ADJUSTED ? I LIMIT ≤ ? I INDUCTOR
V ITHM(LOW)
R DS(ON)(MIN) = L LM(VALLEY)
R DS(ON)(MIN) = L LM(VALLEY)
A RDS - 1
R DS(ON)(MAX)
0
10
20
30
40
50
AVERAGE INDUCTOR CURRENT (A)
Figure 6. Master/Slave Current-Limit Thresholds
? ?
Unadjusted ? I LIMIT ITHM ( HIGH ) ?
= V
?
When unadjusted, the on-resistance variation of the
low-side MOSFETs results in a maximum current-limit
variation ( ? I LIMIT ) determined by the following equation:
A RDS ? 1
? R DS ( ON )( MAX ) ?
where A RDS = R DS(ON)(MAX) /R DS(ON)(MIN) . Using the
MAX1887/MAX1897 to adjust the master ’ s current-limit
threshold results in a maximum current-limit variation
less than the peak-to-peak inductor current:
Adjusted ? I LIMIT ≤ ? I INDUCTOR
rent-limit variation from 21.7A (unadjusted) to less than
6.4A (adjusted).
Output Capacitor Selection
The output filter capacitor must have low enough effec-
tive series resistance (ESR) to meet output ripple and
load-transient requirements, yet have high enough ESR
to satisfy stability requirements.
In CPU V CORE converters and other applications where
the output is subject to large load transients, the output
capacitor selection typically depends on how much
ESR is needed to prevent the output from dipping too
low under a load transient. Ignoring the sag due to
finite capacitance:
As shown in Figure 6, the resulting current-limit varia-
tion of the master is dramatically reduced. For the
above example, this control scheme reduces the cur-
R ESR ≤
V STEP
? I LOAD ( MAX )
22
______________________________________________________________________________________
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