Datasheet
PGA308
www.ti.com
SBOS440B –JULY 2008–REVISED DECEMBER 2010
ELECTRICAL CHARACTERISTICS
Boldface limits apply over the specified temperature range, T
A
= –40°C to +125°C.
At T
A
= +25°C, V
S
= +5V, GND = 0V, D
OUT
/V
CLAMP
= +5V, and V
REF
= +5V, unless otherwise noted.
PGA308
PARAMETER CONDITIONS MIN TYP MAX UNIT
V
OUT
/V
IN
Differential Signal Gains
(1)
Front-End PGA gains (G
F
): 4, 6, 8, 12, 16, 32, 64, 100, 200, 2.67 9600
(Front-End PGA + Output Amplifier) 400, 480, 600, 800, 960, 1200, 1600
V/V
Output Amplifier gains: 2, 2.4, 3, 3.6, 4, 4.5, 6
Fine Gain Adjust = 0.33 to 1
V
OUT
/V
IN
Slew Rate CMP_SEL [CFG1 register] = 0 0.6
V/ms
(Front-End PGA + Output Amplifier)
CMP_SEL [CFG1 register] = 1 0.3 V/ms
V
OUT
/V
IN
Settling Time (0.01%FSR) V
OUT
/V
IN
differential gain = 8, 13
ms
(Front-End PGA + Output Amplifier) V
OUT
= +0.5V to +4.5V step, comp off, no capacitive load
V
OUT
/V
IN
differential gain = 200, 15
ms
V
OUT
= +0.5V to +4.5V step, comp off, no capacitive load
External Sensor Output Sensitivity
(2)
V
S
= V
REF
= V
CLAMP
= +5V 0.08 296 mV/V
FRONT-END PGA
Auto-Zero Internal Frequency 40 kHz
Offset Voltage (RTI)
(3)
Coarse Offset Adjust disabled ±5 ±40 mV
vs Temperature Coarse Offset Adjust disabled ±0.2 mV/°C
vs Supply Voltage, V
S
Coarse Offset Adjust disabled 2 + 150/G
F
10 + 1000/G
F
mV/V
vs Common-Mode Voltage G
F
= Front-End PGA gain, 1 + 250/G
F
10 + 2000/G
F
mV/V
Coarse Offset Adjust disabled
Offset Voltage Programming Range (RTI)
(3)
Coarse Offset Adjust enabled, –100 100 mV
Coarse Offset Adjust controls offset
vs Temperature Coarse Offset Adjust enabled ±0.2 mV/°C
vs Supply Voltage, V
S
Coarse Offset Adjust enabled 2 + 150/G
F
mV/V
vs Common-Mode Voltage G
F
= Front-End PGA gain, 1 + 250/G
F
mV/V
Coarse Offset Adjust enabled
Linear Input Voltage Range
(4)
0.2 V
S
– 1.4 V
Input Bias Current ±0.3 ±1.5 nA
vs Temperature 10 pA/°C
Input Offset Current ±0.1 ±1.5 nA
vs Temperature 10 pA/°C
Input Impedance: Differential 30 ∥ 6 GΩ ∥ pF
Input Impedance: Common-Mode 50 ∥ 20 GΩ ∥ pF
Input Voltage Noise RTI, dc to 10Hz, G
F
= 100, R
S
= 0Ω 1.2 mV
PP
Input Voltage Noise Density RTI, voltage noise density, f = 1kHz, Coarse Offset Adjust = 50 nV/√Hz
0V
RTI, voltage noise density, f = 1kHz, 80 nV/√Hz
Coarse Offset Adjust = 100mV
Input EMI Filter Frequency f
3dB
Input EMI filter to GND, V
IN1
and V
IN2
40 MHz
PGA Gain
(5)
Gain Range Steps 4, 6, 8, 12, 16, 32, 64, 100, 200, 400, 480, 600, 800, 960, 4 1600 V/V
1200, 1600
Initial Gain Error G
F
≤ 16 ±0.03 ±0.25 %
32 ≤ G
F
≤ 480 ±0.1 ±0.4 %
600 ≤ G
F
≤ 1600 ±0.3 ±1 %
vs Temperature 6 ppm/°C
Output Voltage Range 0.05 V
S
– 0.05 V
Bandwidth G
F
= 4 400 kHz
G
F
= 1600 10 kHz
(1) PGA308 total differential gain from input (V
IN1
– V
IN2
) to output (V
OUT
): V
OUT
/ (V
IN1
– V
IN2
) = (PGA gain) × (output amplifier gain) × (fine
gain adjust) with output amplifier internal gains used.
(2) Based on bridge sensor excitation voltage of +5V and PGA308 output voltage span of 4V. Individual applications must consider noise,
small-signal bandwidth, and required system error to assess if the PGA308 will work for a given sensor sensitivity.
(3) RTI = Referred-to-input.
(4) Linear input range is the allowed min/max voltage on the V
IN1
and V
IN2
pins for the front-end PGA to continue to operate in a linear
region. The allowed common-mode and differential voltage depends on gain and offset settings. Refer to the PGA308 User's Guide
(SBOU069), for more information.
(5) I
REF
current load is typically 100mA while in Shutdown mode. Although the output amplifier is disabled in Shutdown mode, RFO and
RGO (180kΩ typical total) remain connected in series between V
FB
and GND while in Shutdown mode. See Figure 37, Detailed Block
Diagram, for more information.
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