Time(400 s/div)

m

V

IN

0.1 F

m

1 F

m

10 F

m

V

IN

REF33xx

GND

V

OUT

1.2V

Bandgap

REF33xx

V

IN

V

OUT

V

OUT

V

IN

C

BYPASS

1 Fto10 F

(recommended)

m

m

C

L

0.1 Fto10 F

m

m

GND

11

REF3312, REF3318, REF3320, REF3325, REF3330, REF3333

www.ti.com

SBOS392H – AUGUST 2007 – REVISED AUGUST 2019

Product Folder Links: REF3312 REF3318 REF3320 REF3325 REF3330 REF3333

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Copyright © 2007–2019, Texas Instruments Incorporated

9 Detailed Description

9.1 Overview

The REF33xx is a family of low-power, precision band-gap voltage references that are specifically designed for

extremely low dropout, excellent initial voltage accuracy with a high output current. A simplified block diagram of

the REF33xx is shown in the Functional Block Diagram section. Figure 17 shows the typical connections for the

REF33xx. A supply bypass capacitor ranging between 1 μF to 10 μF is recommended. The total capacitive load

at the output must be between 0.1 μF to 10 μF to ensure output stability.

Figure 17. Basic Connections

9.2 Functional Block Diagram

9.3 Feature Description

9.3.1 Start-Up Time

The REF33xx features an advanced start-up circuit. Start-up time is almost independent of load (with a 0.1-μF to

10-μF load). Upon startup, the current boost circuit forces the output voltage. When the preset voltage is

reached, the REF33xx switches to the second stage of output circuitry to precisely set the output voltage.

Figure 18 shows the start-up time of the REF3325 for three different capacitive loads. In all three cases, the

output voltage settles within 2 ms.

Figure 18. Start-Up Time