REV. 0

–14–

ADM1070

Figure 13 shows the behavior of ADM1070 when a temporary

current fault occurs followed by a permanent current fault.

When the first overcurrent fault occurs, the first 100 mV spike

fault corrects itself. After this time period, a no fault condition is

detected and the limited consecutive counter is reset. GATE is

reasserted. When the overcurrent fault returns permanently, the

limited consecutive retry counter detects seven consecutive

faults and the part latches off.

GATE

SENSE

5.00V

CH2

100mV

M 500ms

CH1

T

In this way, the ADM1070 prevents nuisance shutdowns from

transient shorts of up to three seconds (typically), but will provide

latched shut-down protection from permanently shorted loads.

KELVIN SENSE RESISTOR CONNECTION

When using a low value sense resistor for high current measure-

ment, the problem of parasitic series resistance can arise. The

lead resistance can be a substantial fraction of the rated resis-

tance, making the total resistance a function of lead length. This

problem can be avoided by using a Kelvin sense connection.

This type of connection separates the current path through

the resistor and the voltage drop across the resistor. Figure 14

shows the correct way to connect the sense resistor between the

KELVIN SENSE TRACES

CURRENT

FLOW FROM

LOAD

CURRENT

FLOW TO –48V

BACKPLANE

SENSE RESISTOR

SENSE

ADM1070

Figure 14. Kelvin Sensing with the ADM1070

UV/OV AS ENABLE PIN

Connecting an open collector output to the UV/OV Pin means

that a TTL signal can be used to disable the part. In Figure 15,

the open collector output connects to

EN. Driving the base of

the open collector device high enough to cause the UV/OV Pin

to be pulled below the undervoltage falling threshold of 0.86 V

typical will cause the pass transistor Q1 to be turned off.

EN

ADM1070

0V

–48V

R1

R2

UV/OV

TIMER

GATE

SENSE

Q1

Figure 15. UV/OV Used as Enable Input