LP2980

1 PF

Input

Voltage

ON /OFF

VIN

VOUT

VOUT = 0V to 5V

DAC102S085

DIN

SCLK

SYNC

VA VREFIN

0.1 PF

Copyright © 2016, Texas Instruments Incorporated

LP3985

1 PF

0.1 PF

Input

Voltage

0.01 PF

VOUT = 0V to 5V

DAC082S085

DIN

SCLK

SYNC

VA VREFIN

0.1 PF

Copyright © 2016, Texas Instruments Incorporated

21

DAC082S085

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SNAS365G – MAY 2006 – REVISED JUNE 2016

Product Folder Links: DAC082S085

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Using References as Power Supplies (continued)

•

IZ(max) is the maximum allowable current through the LM4050

•

IZ(min) is the minimum current required by the LM4050 for proper regulation

•

IDAC(max) is the maximum DAC082S085 supply current

(5)

10.1.3 LP3985

The LP3985 is a low-noise, ultra-low dropout voltage regulator with a 3% accuracy over temperature. It is a good

choice for applications that do not require a precision reference for the DAC082S085. It comes in 3-V, 3.3-V, and

5-V versions, among others, and sports a low 30-µV noise specification at low frequencies. Because low

frequency noise is relatively difficult to filter, this specification could be important for some applications. The

LP3985 comes in a space-saving, 5-pin SOT-23 and 5-bump DSBGA packages.

Figure 39. Using the LP3985 Regulator

An input capacitance of 1 µF without any ESR requirement is required at the LP3985 input, while a 1-µF ceramic

capacitor with an ESR requirement of 5 m

Ω to 500 mΩ is required at the output. Careful interpretation and

understanding of the capacitor specification is required to ensure correct device operation.

10.1.4 LP2980

The LP2980 is an ultra-low dropout regulator with a 0.5% or 1% accuracy over temperature, depending upon

grade. It is available in 3-V, 3.3-V, and 5-V versions, among others.

Figure 40. Using the LP2980 Regulator

Like any low dropout regulator, the LP2980 requires an output capacitor for loop stability. This output capacitor

must be at least 1-µF over temperature, but values of 2.2 µF or more provide even better performance. The ESR

of this capacitor must be within the range specified in the LP2980 data sheet. Surface-mount solid tantalum

capacitors offer a good combination of small size and ESR. Ceramic capacitors are attractive due to their small

size but generally have ESR values that are too low for use with the LP2980. Aluminum electrolytic capacitors

are typically not a good choice due to their large size and have ESR values that may be too high at low

temperatures.