9

LT1460S3 (SOT-23)

Hysteresis

Hysteresis data shown in Figure 5 and Figure 6 represents

the worst-case data taken on parts from 0

°C to 70°C and

from – 40

°C to 85°C. The output is capable of dissipating

17.5V • 20mA = 350mW. The thermal resistance of the

SOT-23 package is 325

°C/W and this dissipation causes

a 114

°C internal rise producing a junction temperature of

cause the output to shift due to thermal hysteresis. For

highest performance in precision applications, do not

let the LT1460S3’s junction temperature exceed 85

°C.

Fast Turn-On

It is recommended to add a 0.1

µF or larger bypass

capacitor to the input pin of the LT1460S3s. Although this

can help stability with large load currents, another reason

is for proper start-up. The LT1460S3 can start in 10

µs, but

it is important to limit the dv/dt of the input. Under light

load conditions and with a very fast input, internal nodes

overslew and this requires finite recovery time. Figure 8

shows the result of no bypass capacitance on the input and

no output load on the LT1460S3-5. In this case the supply

dv/dt is 7.5V in 30ns which causes internal overslew, and

the output does not bias to 5V until 40

µs after turn-on.

Although 40

µs is a typical turn-on time, it can be much

longer. Figure 9 shows the effect of a 0.1

µF bypass

capacitor which limits the input dv/dt to approximately

7.5V in 20

µs. The part always starts quickly.

Figure 6. 0

°C to 70°C Hysteresis

Figure 7. – 40

°C to 85°C Hysteresis

20

µs/DIV

0V

0V

7.5V

1460S3 F08

20

µs/DIV

0V

7.5V

1460S3 F08

HYSTERESIS (ppm)

–240

–160

– 80

0

8

70

°C TO 25°C0°C TO 25°C

10

12

1460S3 F06

6

4

80

160

–200

–120

–40

40

120

200

2

0

18

16

14

240

WORST-CASE HYSTERESIS

ON 40 UNITS

HYSTERESIS (ppm)

–600

–400

–200

0

4

85

°C TO 25°C–40°C TO 25°C

5

6

1460S3 F07

3

2

200

400

–500

–300

–100

100

300

500

1

0

9

8

7

600

WORST-CASE HYSTERESIS

ON 34 UNITS