REF6025 Datasheet, PDF (21/37 Pages) Texas Instruments – High-Precision Voltage Reference With Integrated ADC Drive Buffer

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REF6025, REF6030, REF6033, REF6041, REF6045, REF6050
SBOS708B – MAY 2016 – REVISED AUGUST 2016
Feature Description (continued)
The REF60xx family of voltage references have an integrated low output impedance buffer (ADC drive buffer);
therefore, there is no need for an external buffer while driving the REF pin of high-precision, high-throughput
SAR ADCs, as shown in Figure 50. The ADC drive buffer of the REF60xx is capable of replenishing a charge of
70 pC on a 47-µF capacitor in 1 µs, without allowing the voltage on the capacitor to droop more than 1 LSB at
18-bit precision. The REF60xx are trimmed at multiple temperatures in production, achieving a max drift of just 5
ppm/°C for both the voltage reference and the buffer combined, while operating at a typical quiescent current of
820 µA. Figure 51 compares the output impedance of a regular voltage reference (REF20xx) and a voltage
reference with integrated ADC drive buffer (REF60xx). Figure 52 compares the burst-mode, reference-settling
performance of a regular voltage reference and the REF60xx.
Power Supply
VIN
EN
Bandgap
Voltage
Reference
REF60xx
RFILT
RLIM = 120 NŸ
SS
OUT_S
VIN
Buffer
+
OUT_F
RESR = 5 PŸ
GND_S
FILT
GND_F
CFILT = 1 µF
CL = 47 µF
R = 1 NŸ
VIN
R = 1 NŸ
R = 1 NŸ
Power Supply
+
THS4521
RF = 5 Ÿ
CF = 10 nF
RF = 5 Ÿ
GND
AINP
REF
AINN
ADS8881
R = 1 NŸ
Copyright © 2016, Texas Instruments Incorporated
Figure 50. REF60xx Driving REF Pin of ADS8881 SAR ADC
100
10
1
0.1
0.01
0.001
100
REF20xx (C_L = 10 µF)
REF60xx (C_L = 10 µF)
1k
10k
100k
1M
Frequency (Hz)
C063
Figure 51. Output Impedance Comparison
4
3
2
1
0
±1
±2
±3
±4
0
Regular Voltage Reference Droop
REF60xx Droop
200
400
600
800
1000
Time (µs)
C042
1 LSB = 19.07 µV, with ADS8881 at 1 MSPS
Figure 52. Reference Droop Comparison
Copyright © 2016, Texas Instruments Incorporated
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Product Folder Links: REF6025 REF6030 REF6033 REF6041 REF6045 REF6050