© 2013 Littelfuse, Inc.

Specifications are subject to change without notice.

Revised: 04/24/13

General Purpose ESD Protection - SP721 Series

Peak Transient Current Capability of the SP721

The peak transient current capability rises sharply as the

width of the current pulse narrows. Destructive testing

was done to fully evaluate the SP721’s ability to withstand

a wide range of peak current pulses vs time. The circuit

used to generate current pulses is shown in Figure 4.

The test circuit of Figure 4 is shown with a positive pulse

input. For a negative pulse input, the (-) current pulse input

goes to an SP721 ‘IN’ input pin and the (+) current pulse

input goes to the SP721 V- pin. The V+ to V- supply of the

SP721 must be allowed to float. (i.e., It is not tied to the

ground reference of the current pulse generator.) Figure

5 shows the point of overstress as defined by increased

leakage in excess of the data sheet published limits.

The maximum peak input current capability is dependent

on the ambient temperature, improving as the temperature

is reduced. Peak current curves are shown for ambient

temperatures of 25ºC and 105ºC and a 15V power supply

condition. The safe operating range of the transient peak

current should be limited to no more than 75% of the

measured overstress level for any given pulse width as

shown in the curves of Figure 5.

Note that adjacent input pins of the SP721 may be

paralleled to improve current (and ESD) capability. The

sustained peak current capability is increased to nearly

twice that of a single pin.

+

-

VOLTAGE

PROBE

+

-

(-)

(+)

C1 ~ 100 µF

C1

VARIABLE TIME DURATION

CURRENT PULSE GENERA TOR

1

2

3

4

8

7

6

5

V+

IN

IN

IN

IN

IN

IN

V-

SP721

CURRENT

SENSE

FIGURE 5. TYPICAL SP721 PEAK CURRENT TEST CIRCUIT

WITH A VARIABLE PULSE WIDTH INPUT

0.001

0.01

0.1

1

10

7

6

5

4

3

2

1

0

100

1000

CAUTION: SAFE OPERATING CONDITIONS LIMIT

THE MAXIMUM PEAK CURRENT FOR A GIVEN

PULSE WIDTH TO BE NO GREATER THAN 75%

OF THE VALUES SHOWN ON EACH CURVE.

V+ TO V-SUPPLY = 15V

T

T

PULSE WIDTH TIME (ms)

Showing the Measured Point of Overstress in Amperes vs

pulse width time in milliseconds

Figure 5: SP721 Typical Single Peak Current Pulse

Capability

Figure 4: Typical SP721 Peak CurrentTest Circuit

with a Variable Pulse Width Input