MAX4792 查看數據表（PDF） - Maxim Integrated

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MAX4792

200mA/250mA/300mA Current-Limit Switches

Maxim Integrated 

200mA/250mA/300mA Current-Limit Switches

tBLANK

tBLANK

LOAD

CURRENT

ON

SWITCH

STATUS

OFF

ON PIN

VOLTAGE

FLAG PIN

STATUS

LOAD

CURRENT

tBLANK

(a)

tBLANK

ON

SWITCH

STATUS

OFF

IN PIN

VOLTAGE

UVLO

FLAG PIN

STATUS

(b)

Figure 3. MAX4789/MAX4791/MAX4793 Latch-Off Fault

Blanking

Applications Information

Input Capacitor

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.

Output Capacitance

Connect a 0.1µF capacitor from OUT to GND. This

capacitor helps prevent inductive parasitics from

pulling OUT negative during turn-off, thus preventing

the MAX4789–MAX4794 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:

CMAX < IFWD_MIN

× tBLANK _MIN

VIN

Layout and Thermal Dissipation

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:

PMAX =

VIN_MAX × IOUT_MAX ×

tRETRY + tBLANK

tBLANK

= 302mW

where VIN = 5.5V, IOUT = 450mA, tBLANK = 14ms, and

tRETRY = 98ms.

Attention must be given to the MAX4789, MAX4791,

and MAX4793 where the latch-off condition must be

manually reset by toggling ON from high to low. If the

latch-off time duration is not sufficiently high, it is possi-

ble for the device to reach the thermal-shutdown

threshold and never be able to turn the device on until it

cools down.

Chip Information

PROCESS: BiCMOS

8 _______________________________________________________________________________________

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