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LT1790

1790fb

APPLICATIONS INFORMATION

Bypass and Load Capacitors

The LT1790 voltage references should have an input bypass

capacitor of 0.1μF or larger, however the bypassing of other

local devices may serve as the required component. These

references also require an output capacitor for stability.

The optimum output capacitance for most applications

is 1μF, although larger values work as well. This capaci-

tor affects the turn-on and settling time for the output to

reach its ﬁnal value.

All LT1790 voltages perform virtually the same, so the

LT1790-2.5 is used as an example.

Figure 1 shows the turn-on time for the LT1790-2.5 with a

1μF input bypass and 1μF load capacitor. Figure 2 shows

the output response to a 0.5V transient on VIN with the

same capacitors.

The test circuit of Figure 3 is used to measure the stability

of various load currents. With RL=1k,the1Vstepproduces

a current step of 1mA. Figure 4 shows the response to a

± 0.5mA load. Figure 5 is the output response to a sourcing

step from 4mA to 5mA, and Figure 6 is the output response

of a sinking step from –4mA to –5mA.

Figure 1. Turn-On Characteristics of LT1790-2.5

Figure 2. Output Response to 0.5V Ripple on VIN

Figure 3. Response Time Test Circuit

Figure 4. LT1790-2.5 Sourcing and Sinking 0.5mA

Figure 5. LT1790-2.5 Sourcing 4mA to 5mA

LT1790-2.5

CIN

0.1μF

1μF

VGEN

1790 F03

VIN

1, 2

1790 F01

VIN

VOUT

1790 F02

VIN

VOUT

1790 F04

VGEN

VOUT

(AC COUPLED)

1790 F05

VGEN

VOUT

(AC COUPLED)

–3V

–2V

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