2.13.4 Analog Bipolar Prescaler (ABPS)

With the ABPS set to its high range setting (GDEC = 00), a hypothetical input voltage in the range –15.36V to +15.36V is scaled and offset by the ABPS input amplifier to match the ADC full range of 0V to 2.56V using a nominal gain of –0.08333V/V. However, due to reliability considerations, the voltage applied to the ABPS input should never be outside the range of –11.5V to +14.4V, restricting the usable ADC input voltage to 2.238V to 0.080V and the corresponding 12-bit output codes to the range of 3581 to 128 (decimal), respectively.

Unless otherwise noted, ABPS performance is specified at 25 °C with nominal power supply voltages, with the output measured using the internal voltage reference with the internal ADC in 12-bit mode and 100 KHz sampling frequency, after trimming and digital compensation; and applies to all ranges.

Table 2-97. ABPS Performance Specifications
SpecificationTest ConditionsMin.Typ.Max.Units
Input voltage range (for driving ADC over its full range)GDEC[1:0] = 11—±2.56—V
GDEC[1:0] = 10—±5.12—V
GDEC[1:0] = 01—±10.24—V
GDEC[1:0] = 00 (limited by maximum rating)—See note 1—V
Analog gain (from input pad to ADC input)GDEC[1:0] = 11—–0.5—V/V
GDEC[1:0] = 10—–0.25—V/V
GDEC[1:0] = 01—–0.125—V/V
GDEC[1:0] = 00—–0.0833—V/V
Gain error–2.8–0.40.7%
–40ºC to +100ºC–2.8–0.40.7%
–55ºC to +125ºC–4–0.44%
Input referred offset voltage
GDEC[1:0] = 11–0.31–0.070.31% FS1
–55ºC to +125ºC–1.7—1.7% FS1
GDEC[1:0] = 10–0.34–0.070.34% FS1
–55ºC to +125ºC–1.6—1.6% FS1
GDEC[1:0] = 01–0.61–0.070.35% FS1
–55ºC to +125ºC–1.6—1.6% FS1
GDEC[1:0] = 00–0.39–0.070.35% FS1
–55ºC to +125ºC–1.6—1.6% FS1
SINAD5356—dB
Non-linearityRMS deviation from BFSL——0.5% FS1
Effective number of bits (ENOB)
Figure 2-54. EQ 11
GDEC[1:0] = 11
(±2.56 range), –1 dBFS input
12-bit mode 10 KHz8.69.1—Bits
12-bit mode 100 KHz8.69.1—Bits
10-bit mode 10 KHz8.58.9—Bits
10-bit mode 100 KHz8.58.9—Bits
8-bit mode 10 KHz7.77.8—Bits
8-bit mode 100 KHz7.77.8—Bits
Large-signal bandwidth–1 dBFS input—1—MHz
Analog settling timeTo 0.1% of final value (with ADC load)——10µs
Input resistance——1—MΩ
Power supply rejection ratioDC (0–1 KHz)3840—dB
ABPS power supply current requirements (not including ADC or VAREFx)ABPS_EN = 1 (operational mode)
VCC33A—123134µA
VCC33AP—8994µA
VCC15A—1—µA
Note:
  1. FS is full-scale error, defined as the difference between the actual value that triggers the transition to full-scale and the ideal analog full-scale transition value. Full-scale error equals offset error plus gain error. Refer to the Analog-to-Digital Converter chapter of the SmartFusion Programmable Analog User’s Guide for more information.