參數(shù)資料
型號(hào)： MAX4785EXS-T
廠商： MAXIM INTEGRATED PRODUCTS INC
元件分類： 模擬信號(hào)調(diào)理
英文描述： 50mA/100mA Current-Limit Switches
中文描述： SPECIALTY ANALOG CIRCUIT, PDSO4
封裝： EIAJ, SC-70, 4 PIN
文件頁數(shù)： 7/10頁
文件大?。?/td> 266K
代理商： MAX4785EXS-T
FLAG
Indicator
The MAX4785 and MAX4787 feature a latched fault out-
put,
FLAG
. Whenever a fault is activated, it latches
FLAG
output low and also turns the switch off.
FLAG
is
an open-drain output transistor and requires an exter-
nal pullup resistor from
FLAG
to IN. During shutdown
(ON is low), the pulldown on
FLAG
output is released in
order to limit power dissipation.
FLAG
goes low when
any of the following conditions occur:
The die temperature exceeds the thermal-shutdown
temperature limit of +150
°
C.
The device is in current limit for more than the fault-
blanking period.
V
IN
is below UVLO threshold.
Autoretry (MAX4786/MAX4788)
When the forward or reverse current-limit threshold is
exceeded, t
BLANK
timer begins counting (Figure 2).
The timer resets if the overcurrent condition disappears
before t
BLANK
has elapsed. A retry time delay, t
RETRY
,
is started immediately after t
BLANK
has elapsed and
during that time, the switch is latched off. At the end of
t
RETRY
, the switch is turned on again. If the fault still
exists, the cycle is repeated. If the fault has been
removed, the switch stays on.
The autoretry feature saves system power in the case
of an overcurrent or short-circuit condition. During
t
BLANK
, when the switch is on, the supply current is at
the current limit. During t
RETRY
, when the switch is off,
the current through the switch is zero. Instead of
observing the full load current, the switch sees the
equivalent load current times duty cycle or I
SUPPLY
=
I
LOAD
t
BLANK
/(t
BLANK
+ t
RETRY
). With a typical
t
BLANK
= 37ms and typical t
RETRY
= 259ms, the duty
cycle is 12%, which results in an 88% power savings
over the switch being on the entire time. The duty cycle
is consistent across the process and devices.
Latch Off (MAX4785/MAX4787)
When the forward or reverse current-limit threshold is
exceeded, t
BLANK
timer begins counting. The timer
resets if the overcurrent condition disappears before
t
BLANK
has elapsed. The switch is shut off if the over-
current condition continues up to the end of the blank-
ing time. Reset the switch by either toggling ON (Figure
3a) or cycling the input voltage below UVLO, typically
2V (Figure 3b).
Fault Blanking
The MAX4785
–
MAX4788 feature 14ms (min) fault
blanking. Fault blanking allows current-limit faults,
including momentary short-circuit faults that occur
when hot swapping a capacitive load, and also ensures
that no fault is issued during power-up. When a load
transient causes the device to enter current limit, an
internal counter starts. If the load-transient fault persists
beyond the fault-blanking timeout, the MAX4785 and
MAX4787s
’
FLAG
asserts low. Load-transient faults less
than t
BLANK
do not cause a
FLAG
output assertion.
Only current-limit faults are blanked.
A thermal fault and input voltage drops below the
UVLO threshold cause
FLAG
to assert immediately and
do not wait for the blanking time.
Thermal Shutdown
The MAX4785
–
MAX4788 have a thermal shutdown fea-
ture to protect the devices from overheating. The switch
turns off and
FLAG
goes low immediately (no fault blank-
ing) when the junction temperature exceeds +150
°
C.
M
50mA/100mA Current-Limit Switches
_______________________________________________________________________________________
7
ON
Low
High
High
FAULT
X
SWITCH ON/OFF
SUPPLY CURRENT MODE
Shutdown
Shutdown
Latch off
Latch off
OFF
OFF
OFF immediately (t
BLANK
period does not apply)
OFF after t
BLANK
period has elapsed
ON during t
BLANK
period, OFF during t
RETRY
period for the
MAX4786 and MAX4788; cycle repeats until fault is removed
Undervoltage lockout
Thermal
High
Current limit
See the
Autoretry
section
Table 1. MAX4785–MAX4788 Switch Truth Table
LOAD
CURRENT
SWITCH
STATUS
t
BLANK
OFF
ON
t
RETRY
CURRENT
LIMIT
SHORT
CONDITION
REMOVED
t
BLANK
t
BLANK
Figure 2. MAX4786/MAX4788 Autoretry Fault Blanking Diagram
相關(guān)PDF資料
PDF描述
MAX4786EXS-T 50mA/100mA Current-Limit Switches
MAX4787EXK-T 50mA/100mA Current-Limit Switches
MAX4787EXS-T 50mA/100mA Current-Limit Switches
MAX4788EXS-T 50mA/100mA Current-Limit Switches
MAX4785 LOW-POWER RS-485 FULL-DUPLEX DRIVERS/RECEIVERS 10-MSOP -40 to 85
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX4786EXS 制造商:Maxim Integrated Products 功能描述:50MA/100MA CURRENT-LIMIT SWITCHES - Cut Tape Product
MAX4786EXS+ 制造商:Maxim Integrated Products 功能描述:CURRENT LIMIT SW 1-IN 1-OUT 2.3V TO 5.5V 0.12A 4PIN SC-70 - Cut Tape Product
MAX4786EXS+T 功能描述:電源開關(guān) IC - 配電 50mA/100mA Current Limit Switch RoHS:否 制造商:Exar 輸出端數(shù)量:1 開啟電阻（最大值）:85 mOhms 開啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5
MAX4786EXS-T 功能描述:電源開關(guān) IC - 配電 RoHS:否 制造商:Exar 輸出端數(shù)量:1 開啟電阻（最大值）:85 mOhms 開啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5
MAX4787EKIT+ 功能描述:電源開關(guān) IC - 配電 50mA/100mA Current-Limit Switches RoHS:否 制造商:Exar 輸出端數(shù)量:1 開啟電阻（最大值）:85 mOhms 開啟時(shí)間（最大值）:400 us 關(guān)閉時(shí)間（最大值）:20 us 工作電源電壓:3.2 V to 6.5 V 電源電流（最大值）: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOT-23-5
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