000-0046140-111
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SLG46140
9.3.2 PGA Output
PGA can be used either in standalone mode or as ADC font-end / ACMP input buffer.
In PGA standalone mode (ADC in POWER DOWN mode) PGA output is always referenced to GND. When ADC is powered on,
it powers also the PGA output reference macrocell, so that the output voltage is referenced to one of predefined output offset
voltages Vos(RTO) which can be found in PGA specifications. This offset is required for correct ADC operation and it does not
affect output code calculation.
PGA output reference (when ADC is on):
•
Single-ended mode: Vos(RTO) = GND
•
Differential mode: Vos(RTO) = 550 mV
•
Pseudo-Differential mode: Vos(RTO) = 180 mV
Note that the reference voltage macrocell is controlled by ADC, therefore if ADC is in POWER DOWN mode, the reference
macrocell is OFF and PGA output is referenced to GND. In this case both Differential and Pseudo-Differential modes provide the
same output. Typical PGA specifications in Differential/Pseudo-Differential mode with ADC in POWER DOWN state are given in
specifications section for information only.
Note 1: PGA operation in Differential/Pseudo-Differential mode with ADC in POWER DOWN state is not recommended to use.
Note 2: Toggling ADC POWER DOWN mode will also toggle the PGA output reference macrocell, that will influence the ACMP
input voltage.
PGA has a few output connection possibilities: to ACMP1 and/or ADC, and to external output on PIN4. Connection to external
output is possible only when ADC is powered down.
PGA output connection options:
•
Single-Ended mode:
• ADC
• ACMP
• External output
•
Differential mode:
• ADC
• ACMP (See Note 2)
• External output (Operation in this mode is not recommended)
•
Pseudo-Differential mode:
• ADC
• ACMP (See Note 2)
• External output (Operation in this mode is not recommended)
9.3.3 PGA Power On Signal
Whenever ADC is enabled, PGA is powered on automatically. However, it is possible to use PGA separately. In this case, Power
On function must be enabled, reg <535> = 1.
9.3.4 PGA Register Settings
Table 34. PGA Register Settings
Signal Function
Register Bit
Address
Register Definition
PGA Native Input From
Internal DAC0
<529>
0: Disable
1: Enable