Datasheet

V = mux_sign V + V GI + V GD GO
OUT IN Coarse_Offset Zero_DAC
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PGA308
SBOS440B –JULY 2008–REVISED DECEMBER 2010 www.ti.com
OTP MEMORY BANKS PGA308 TRANSFER FUNCTION
There are four one-time programmable (OTP) bank Equation 1 shows the mathematical expression that is
selection registers: BANK SEL1, BANK SEL2, BANK used to compute the output voltage, V
OUT
. This
SEL3, and BANK SEL4. Bank selection may be set equation can also be rearranged algebraically to
four times by programming the BANK SELx registers solve for different terms. For example, during
in order (1, 2, 3, 4). The default OTP bank used on calibration, this equation is rearranged to solve for
POR is the location stored in the last programmed V
IN
.
BANK SELx register. Therefore, if programmed,
BANK SEL4 always has priority over lower-numbered
(1)
bank select registers.
Where:
The PGA308 contains seven OTP user memory
mux_sign: This term changes the polarity of the
banks. All seven of these banks may be
input signal; value is ±1
independently programmed. However, the default
bank at POR can be set only four times. The seven
V
IN
: The input signal for the PGA308; V
IN
1 = V
INP
,
possible OTP user memory banks allow an end
V
IN
2 = V
INN
product with a microcontroller interface between the
V
Coarse_Offset
: The coarse offset DAC output
end-user and the PGA308 to select from up to seven
voltage
factory pre-programmed configurations. It also
GI: Input stage gain
provides total user flexibility for any other
V
Zero_DAC
: Zero DAC output voltage
configuration through software communication over
the One-Wire interface (1W pin). This flexibility allows
GD: Gain DAC
no-scrap recovery from miscalibration situations.
GO: Output stage gain
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