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LM4040
PRECISION MICROPOWER SHUNT VOLTAGE REFERENCE
SLOS456J 鈥?JANUARY 2005 鈥?REVISED SEPTEMBER 2006
APPLICATION INFORMATION
Start-Up Characteristics
R
S
V
IN
1-Hz Rate
LM4040
V
Z
Figure 7. Test Circuit
Output Capacitor
The LM4040 does not require an output capacitor across cathode and anode for stability. However, if an output
bypass capacitor is desired, the LM4040 is designed to be stable with all capacitive loads.
SOT-23 Connections
There is a parasitic Schottky diode connected between pins 2 and 3 of the SOT-23 packaged device. Thus, pin
3 of the SOT-23 package must be left floating or connected to pin 2.
Use With ADCs or DACs
The LM4040x-41 is designed to be a cost-effective voltage reference as required in 12-bit data-acquisition
systems. For 12-bit systems operating from 5-V supplies such as the ADS7842 (see
Figure 8),
the LM4040x-41
(4.096 V) permits operation with an LSB of 1 mV.
ADS7842
0 V to V
REF
5V
1 AIN0
2 AIN1
3 AIN2
909
+
LM4040A-41
2.2
碌F
4 AIN3
5 V
REF
6 AGND
7 DB11
8 DB10
9 DB9
10 DB8
11 DB7
12 DB6
13 DB5
14 DGND
V
ANA
V
DIG
28
27
5-V Analog Supply
10
碌F
+
0.1
碌F
+
A1 26
A0 25
CLK 24
BUSY
WR
CS
RD
23
22
21
20
Read Input
3.2-MHz Clock
BUSY Output
Write Input
DB0 19
DB1 18
DB2 17
DB3 16
DB4 15
Figure 8. Data-Acquisition Circuit With LM4040x-41
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