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參數(shù)資料
| 型號： | MAX8540 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Synchronizable. High-Frequency Current- and Voltage-Mode PWM Controllers for Isolated Supplies |
| 中文描述： | 可同步、高頻、電流或電壓模式PWM控制器，用于隔離電源 |
| 文件頁數(shù)： | 9/16頁 |
| 文件大?。?/td> | 328K |
| 代理商： | MAX8540 |
Detailed Description
Overvoltage Threshold
The MAX8540/MAX8541 include an overvoltage protec-
tion (OVP) feature that turns off the external MOSFET
when the input voltage exceeds the user-set threshold.
Connect a resistor-divider from the system input to
GND with OV connected to the center to set the OVP
trip point. The threshold voltage for OV is 3.021V (typ):
where V
OV
is the OV threshold, V
IN(MAX)
is the overvolt-
age trip point, R1 is the resistor from the system input
to OV, and R2 is the resistor from OV to GND.
Undervoltage Threshold
The MAX8540/MAX8541 also include an undervoltage
(UV) sensing input. The IC holds the external MOSFET
low until UV reaches its threshold (1.25V typ). Once the
threshold has been reached, the circuit enters soft-start
and brings the output into regulation. Connect a resistor-
divider from the system input to GND with UV at the cen-
ter to set the undervoltage protection (UVP) trip point.
where V
UV
is the UV threshold, V
IN(MIN)
is the UV trip
point, R3 is the resistor from the system input to UV,
and R4 is the resistor from UV to GND.
An alternate method used in the application circuits for
setting the OV and UV trip points is demonstrated in
Figure 1. Use 36.5k
for the bottom resistor (RC). RA
and RB are calculated as follows:
where V
IN(MIN)
is the UV trip point, V
IN(MAX)
is the OV
trip point, V
UV
is the UV threshold (1.25V typ), and V
OV
is the OV threshold (3.021V typ). RA should consist of
two equal-value resistors in series to protect against
single-point failure.
Switching Frequency and Synchronization
The MAX8540/MAX8541 oscillator operates in two
modes: stand-alone or synchronized (sync). A single
input, FREQ/SYNC, doubles as the attachment point for
the frequency-programming resistor and as the syn-
chronization input. The mode recognition is automatic,
based on the signal applied to FREQ/SYNC.
In stand-alone mode, an external resistor connected
from FREQ/SYNC to GND sets the operating frequency.
A 1.25V source is internally applied to FREQ/SYNC and
the oscillator frequency is proportional to the current
out of FREQ/SYNC through the programming resistor.
RA
RC
V
V
RB
RC
IN MIN
(
UV
=
×
)
RB
RC
V
V
V
V
OV
IN MIN
(
UV
IN MAX
(
=
×
×
×
)
)
1
V
R
R
R
V
IN MIN
(
UV
)
=
+
×
3
4
4
V
R
R
R
V
IN MAX
(
OV
)
=
+
×
1
2
2
M
Synchronizable, High-Frequency Current- and
Voltage-Mode PWM Controllers for Isolated Supplies
_______________________________________________________________________________________
9
Table 1. Typical Specifications of UV/OV
and the Actual On/Off Hysteresis of Input
Voltage
UV VOLTAGE
SPECIFICATIONS
(V)
V
IN
OFF
WINDOW (LTP)
(V)
V
IN
ON
WINDOW (UTP)
(V)
MIN
TYP
MAX
MIN
TYP
MAX
1.083
1.128
1.173
1.200
1.250
1.300
29.76
31.00
32.24
—
32.97
34.34
36.00
—
OV VOLTAGE
SPECIFICATIONS
(V)
V
IN
OFF
WINDOW (UTP)
(V)
V
IN
ON
WINDOW (LTP)
(V)
MIN
TYP
MAX
MIN
TYP
MAX
2.901
3.021
3.142
2.778
2.894
3.010
79.70
83.00
86.32
—
76.32
79.50
82.68
—
Assume that 1.250V at UV/OV is scaled to 34.34V for a 48V bus.
R
FREQ/SYNC
(k
)
48.7
19.1
15.8
11.0
8.87
SWITCHING FREQUENCY (kHz)
200
500
600
800
1000
Table 2. Switching Frequency Selection
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX8540EEE | 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 上升時間: 下降時間: 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 |
| MAX8540EEE+ | 功能描述:電流型 PWM 控制器 Synchronizable PWM Controller RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 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 |
| MAX8540EEE+T | 功能描述:電流型 PWM 控制器 PWM Controller Curr-Mode RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時間: 下降時間: 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 |
| MAX8540EEE-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 上升時間: 下降時間: 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 |
| MAX8541EEE | 功能描述:電壓模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
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