LT1790 Linear Technology, LT1790 Datasheet - Page 5

• Manufacturer Part Number: LT1790
• Description: 2.5V Micropower SOT-23 Low Dropout Reference
• Manufacturer: Linear Technology

APPLICATIONS
Bypass and Load Capacitors
The LT1790-2.5 voltage reference should have an input
bypass capacitor of 0.1 F or larger, however the bypass-
ing of other local devices may serve as the required
component. This reference also requires an output capaci-
tor for stability. The optimum output capacitance for most
applications is 1 F, although larger values work as well.
This capacitor affects the turn-on and settling time for the
output to reach its final value.
Figure 1 shows the turn-on time for the LT1790-2.5 with
a 1 F input bypass and 1 F load capacitor. Figure 2 shows
the output response to a 0.5V transient on V
same capacitors.
Figure 2. Output Response to 0.5V Ripple on V
Figure 1. Turn-On Characteristics of LT1790-2.5
3V
2V
1V
0V
3V
2V
1V
0V
U
INFORMATION
U
W
1790 F01
1790 F02
IN
U
V
V
V
V
IN
IN
OUT
IN
OUT
with the
The test circuit of Figure 3 is used to measure the stability
of various load currents. With R
produces a current step of 1mA. Figure 4 shows the
response to a 0.5mA load. Figure 5 is the output re-
sponse to a sourcing step from 4mA to 5mA, and Figure
6 is the output response of a sinking step from – 4mA to
– 5mA.
V
3V
IN
Figure 4. LT1790-2.5 Sourcing and Sinking 0.5mA
V
V
–2V
–3V
GEN
GEN
3V
2V
Figure 5. LT1790-2.5 Sourcing 4mA to 5mA
C
0.1 F
Figure 3. Response Time Test Circuit
IN
4
LT1790-2.5
1, 2
6
C
1 F
L
L
= 1k, the 1V step
LT1790-2.5
1k
1790 F04
1790 F05
V
GEN
V
V
OUT
OUT
1790 F03
1V
5