參數(shù)資料
型號(hào)： MAX1887
廠商： Maxim Integrated Products, Inc.
英文描述： Quick-PWM Slave Controllers for Multiphase, Step-Down
中文描述： Quick-PWM從控制器，用于多相、降壓型電源
文件頁數(shù)： 21/33頁
文件大小： 1018K
代理商： MAX1887
M
Quick-PWM Slave Controllers for
Multiphase, Step-Down Supplies
______________________________________________________________________________________
21
current-limit threshold of 40mV to 150mV. Use 1% toler-
ance resistors in the divider with 10μA to 20μA DC bias
current to prevent significant errors due to the ILIM
pin
’
s input current. Reducing the current-limit threshold
voltage lowers the sense resistor
’
s power dissipation,
but this also increases the relative measurement error:
Now, set the current-limit adjustment ratio (A
ADJ
=
V
ITHM(HIGH)
/V
ITHM(LOW)
) greater than the maximum to
minimum on-resistance ratio (A
RDS
= R
DS(ON)(MAX)
/
R
DS(ON)(MIN)
):
A
A
R
A
B
LIMIT
Increasing A
ADJ
improves the master
’
s current-limit
accuracy but also increases the current limit
’
s noise
sensitivity. Therefore, R
LIMIT
may be selected using the
following equation:
(
(
)(
Finally, verify that the total load on the master
’
s refer-
ence does not exceed 50μA:
Current Limit Design Example
For the typical application circuit shown in Figure 1: V
IN
= 12V, V
OUT
= 1.3V, f
SW
= 300kHz,
η
= 2, I
LOAD(MAX)
= 50A, L = 0.6μH, R
DS(ON)(MAX)
= 6m
, R
DS(ON)(MIN )
= 3m
1) Determine the peak-to-peak inductor current and
the valley current limit:
2) Determine the master
’
s current-limit threshold from
the valley current limit and low-side MOSFETs
’
max-
imum on-resistance over temperature:
V
ITH(MASTER)
≥
21.8A
6m
= 130mV
Now select the resistive-divider values (R
A
and R
B
in Figure 5) to set the appropriate voltage at the
master
’
s ILIM input:
Selecting R
B
= 100k
±1% provides the following
value for R
A
:
3) Determine the slave
’
s current-limit threshold:
Select the resistive-divider values (R
C
and R
D
in
Figure 5) to set the appropriate voltage at the
slave
’
s ILIM input:
Selecting R
D
= 30.1k
±1% provides the following
value for R
A
:
4) Determine R
LIMIT
(Figure 5) from the above equation:
5) Finally, verify that that the total bias currents do not
exceed the 50μA maximum load of the master
’
s ref-
erence:
I
V
k
k
k
V
+
k
k
A
BIAS TOTAL
(
)
//
.
.
=
+
(
)
+
2
54
100
34 8
2
30 1
113
36
μ
R
k
k
3
x m
3
m
m
k
LIMIT
≤
(
)
≈
53 6
100
6
35
.
//
R
V
x
mV
x
k
k
C
=
≈
2
10 42
1
30 1
113
.
R
x
20
mV
A
μ
to
x
mV
A
μ
k
to
k
D
=
=
10 42
10 42
10
21
42
V
m
x
mV
m
6
A
mV
ITHS
≥
+
≈
1 5
.
130
6 4
.
42
R
V
x
mV
x
k
k
A
=
≈
2
10 130
1
100
54
R
x
20
mV
A
μ
to
x
10
mV
A
μ
k
to
k
B
=
=
10 130
10 130
65
130
I
Vx
300
50
2
V
V
Vx
kHzx
2
H
=
A
I
A
x
A
A
INDUCTOR
LIMIT VALLEY
(
=
(
)
=
=
1 3
.
12
1 3
0 6
12
6 4
.
1
6 4
.
21 8
.
.
.
)
μ
I
V
R
R
R
V
R
R
A
BIAS TOTAL
(
REF
B
//
A
LIMIT
REF
C
+
D
)
=
+
(
)
+
≤
50
μ
R
R
R R
R
R
LIMIT
A
DS ON MIN
DS ON MAX
DS ON MIN
(
≤
//
(
)(
)
)
)(
)
//
(
)(
)
(
)(
)
R
R
R
R
ADJ
ROS
DS ON MAX
DS ON MIN
≥
+
≥
1
V
A
R
V
A
R
V
V
R
ILIM SLAVE
(
20
μ
D
ILIM SLAVE
(
10
μ
C
REF MASTER
(
ILIM SLAVE
(
D
)
)
)
)
1
≤
≤
=
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參數(shù)描述
MAX1887EEE 功能描述:電流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX1887EEE+ 功能描述:電流型 PWM 控制器 CDMA Cellular/PCS System Power Supplies RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
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MAX1887EEE-T 功能描述:電流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
MAX1888EUA 功能描述:其他電源管理 RoHS:否 制造商:Texas Instruments 輸出電壓范圍: 輸出電流:4 mA 輸入電壓范圍:3 V to 3.6 V 輸入電流: 功率耗散: 工作溫度范圍:- 40 C to + 110 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-48 封裝:Reel
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