LT1460HCS3-10 Linear Technology, LT1460HCS3-10 Datasheet - Page 9

• Manufacturer Part Number: LT1460HCS3-10
• Description: Family of Micropower Series References in SOT-23
• Manufacturer: Linear Technology

APPLICATIONS
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
relatively high power, i.e., for the LT1460S3-2.5, P
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
T
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.
J
= 25 C + 114 C = 139 C. This elevated temperature will
18
16
14
12
10
6
4
9
8
7
5
4
3
2
0
8
6
2
0
1
–600
–240
WORST-CASE HYSTERESIS
ON 40 UNITS
WORST-CASE HYSTERESIS
ON 34 UNITS
–500
–200
Figure 7. – 40 C to 85 C Hysteresis
–400
–160
Figure 6. 0 C to 70 C Hysteresis
85 C TO 25 C
–300
–120
70 C TO 25 C
U
–200
– 80
HYSTERESIS (ppm)
HYSTERESIS (ppm)
INFORMATION
–100
–40
U
0
0
100
40
W
–40 C TO 25 C
0 C TO 25 C
200
80
120
300
400
160
U
500
200
1460S3 F07
1460S3 F06
600
240
D
=
Fast Turn-On
It is recommended to add a 0.1 F 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 s, 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 s after turn-on.
Although 40 s is a typical turn-on time, it can be much
longer. Figure 9 shows the effect of a 0.1 F bypass
capacitor which limits the input dv/dt to approximately
7.5V in 20 s. The part always starts quickly.
V
V
OUT
OUT
V
V
IN
IN
Figure 9. C
Figure 8. C
LT1460S3 (SOT-23)
20 s/DIV
20 s/DIV
IN
IN
= 0.1 F
= 0 F
1460S3 F08
1460S3 F08
7.5V
0V
0V
7.5V
0V
9