Datasheet

PGA281EVM Hardware www.ti.com
2.4 Input/Output Connections
The PGA281 is a differential input, differential output amplifier. The input signal is applied at BNC
connectors J1 (IN+) and J3 (IN–), while the output signal is measured at BNC connectors J2 (OUT+) and
J4 (OUT–).
2.5 VOCM
VOCM controls the output stage common-mode voltage. On the PGA281EVM, a resistive voltage divider
created by R3 and R4 sets VOCM equal to (VSOP/2).
2.6 Gain Select
Switch S1 controls the PGA281 gain. Each switch channel sets the logic level at the corresponding gain
set pin. When the switch channel is on (up position), G
N
= 1. When the switch channel is off (down
position), G
N
= 0. See Table 5 for all possible gain settings.
Table 5. PGA281 Gain Settings
G3:G0 G4 = 0 G4 = 1
0000 0.125 0.172
0001 0.25 0.344
0010 0.5 0.688
0011 1 1.375
0100 2 2.75
0101 4 5.5
0110 8 11
0111 16 22
1000 32 44
1001 64 88
1010 128 176
1011* 0.125 0.172
1100* 0.125 0.172
1101* 0.125 0.172
1110* 0.125 0.172
1111* 0.125 0.172
2.7 Error Flag
The PGA281 contains circuitry that monitors the integrity of the analog signal at several of the internal
nodes. When signal conditions are outside the linear range, the error flag pin goes active (sets to V
DD
). In
an error condition, LED1 on the PGA281EVM turns on.
Error conditions include:
• Input common-mode range exceeded
• Input clamp active
• Input stage at supply rail
• Input-stage current limit exceeded
• Output stage at supply rail
• Output-stage current limit exceeded
6
PGA281EVM dit.SBOU130–May 2013
Submit Documentation Feedback
Copyright © 2013, Texas Instruments Incorporated