LM4040
PRECISION MICROPOWER SHUNT VOLTAGE REFERENCE
www.ti.com
SLOS456I–JANUARY 2005–REVISED DECEMBER 2005
APPLICATION INFORMATION
Start-Up Characteristics
R
S
V
IN
LM4040
V
Z
1-Hz Rate
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
V
1 AIN0
2 AIN1
3 AIN2
4 AIN3
28
27
5-V Analog Supply
ANA
+
+
5 V
0.1 µF
10 µF
V
DIG
A1 26
A0 25
909
3.2-MHz Clock
BUSY Output
Write Input
V
5
6
7
8
CLK 24
REF
+
2.2 µF
AGND
DB11
DB10
23
22
21
BUSY
WR
LM4040A-41
CS
9
DB9
RD 20
DB0 19
DB1 18
Read Input
10 DB8
11 DB7
12 DB6
13 DB5
14 DGND
DB2 17
DB3 16
DB4 15
Figure 8. Data-Acquisition Circuit With LM4040x-41
25
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