Q3

Q1

Q4

Q7

Q2

Q5

20 pF

20 pF

Q6

Q8

Q12

Q11

Q13

Q10

Q9

Q14

CATHODE

ANODE

500 kΩ

500 kΩ

300 kΩ

200 kΩ

50 kΩ

500 Ω

60 kΩ

100 kΩ

600 kΩ

7.5 kΩ

8

LM285-2.5, LM385-2.5, LM385B-2.5

SLVS023K – JANUARY 1989 – REVISED MARCH 2016

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Product Folder Links: LM285-2.5 LM385-2.5 LM385B-2.5

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Copyright © 1989–2016, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The LMx85-2.5 and LM385B-2.5 devices maintain a nearly constant voltage between the cathode and anode of

2.5 V when the minimum cathode current up to the recommended maximum is provided. See Recommended

Operating Conditions for recommended minimum cathode current.

7.2 Functional Block Diagram

7.3 Feature Description

A band-gap voltage reference controls a high-gain amplifier and shunt pass element to maintain a nearly

constant voltage between the cathode and anode of 2.5 V. Regulation occurs after a minimum current is

provided to power the voltage divider and amplifier. Internal frequency compensation provides a stable loop for

all capacitive loads. Floating shunt design is useful for both positive and negative regulation applications.

7.4 Device Functional Modes

The LMx85-2.5 and LM385B-2.5 devices have a single functional mode. These devices can be used as 2.5-V

fixed voltage references. The reference voltage cannot be adjusted for these devices.

In order for a proper Reverse Voltage to be developed, current must be sourced into the cathode of LM285. The