MAX4787 Maxim, MAX4787 Datasheet - Page 8
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MAX4787
Manufacturer Part Number
MAX4787
Description
The MAX4785-MAX4788 family of switches feature internal
current limiting to prevent host devices from being
damaged due to faulty load conditions
Manufacturer
Maxim
Datasheet
1.MAX4785.pdf
(10 pages)
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The switches with autoretry feature turn back on when
the device temperature drops approximately 15°C. The
switches with latchoff feature require ON cycling.
To limit the input voltage drop during momentary output
short-circuit conditions, connect a capacitor from IN to
GND. A 0.1µF ceramic capacitor is adequate for most
applications; however, higher capacitor values further
reduce the voltage drop at the input and are recom-
mended for lower voltage applications.
Connect a 0.1µF capacitor from OUT to GND. This
capacitor helps prevent inductive parasitics from
pulling OUT negative during turn-off, thus preventing
50mA/100mA Current-Limit Switches
Figure 3. MAX4785/MAX4787 Latch Off Fault Blanking
8
PIN STATUS
PIN STATUS
CURRENT
CURRENT
VOLTAGE
VOLTAGE
SWITCH
SWITCH
STATUS
STATUS
_______________________________________________________________________________________
ON PIN
IN PIN
LOAD
FLAG
LOAD
FLAG
OFF
OFF
ON
ON
Applications Information
t
BLANK
t
BLANK
UVLO
t
(a)
(b)
BLANK
t
BLANK
Output Capacitance
Input Capacitor
the MAX4785–MAX4788 from tripping erroneously. If
the load capacitance is too large, then current may not
have enough time to charge the capacitance and the
device assumes that there is a faulty load condition.
The maximum capacitive load value that can be driven
from OUT is obtained by the following formula:
To optimize the switch response time to output short-
circuit conditions, it is very important to keep all traces
as short as possible to reduce the effect of undesirable
parasitic inductance. Place input and output capacitors
as close as possible to the device (no more than 5mm).
IN and OUT pins must be connected with short traces
to the power bus.
During normal operation, the power dissipation is small
and the package temperature change is minimal. If the
output is continuously shorted to ground at the maxi-
mum supply voltage, the operation of the switches with
the autoretry option does not cause problems because
the total power dissipated during the short is scaled by
the duty cycle:
where V
t
Attention must be given to the MAX4785 and MAX4787
where the latch-off condition must be manually reset by
toggling ON from high to low. If the latch-off time dura-
tion is not sufficiently high, it is possible for the device
to reach the thermal-shutdown threshold and never be
able to turn the device on until it cools down.
RETRY
MAX4785EXS
MAX4785EXK
MAX4786EXS
MAX4787EXS
MAX4787EXK
MAX4788EXS
P
MAX
PART
= 98ms.
IN
=
C
V
MAX
= 5.5V, I
IN MAX
_
Layout and Thermal Dissipation
<
LIMIT (mA)
CURRENT
I
FWD MIN
t
RETRY
OUT
100
100
100
×
50
50
50
_
I
OUT MAX
= 240mA, t
+
_
×
t
V
BLANK
IN
t
FUNCTION
BLANK MIN
Selector Guide
FLAG
Yes
Yes
×
No
No
No
No
BLANK
t
BLANK
_
= 14ms, and
=
161
RETRY
AUTO-
Yes
Yes
No
No
No
No
mW