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TC65 Hardware Interface Description

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TC65_HD_V02.000 Page 71 of 120 08.06.2006

3.16 Analog-to-Digital Converter (ADC)

The ADC of the TC65 consists of 2 independent, unbalanced, multiplexed analog inputs that

can be used for measuring external DC voltages in the range of 0mV…+2400mV. The ADC

has a resolution of 12 bits.

Use the command AT^SRADC described in

[1] to select the analog inputs ADC1_IN or

ADC2_IN, to set the measurement mode and read out the measurement results. The

measured values are indicated in mV.

There is no out of range detection. Voltages beyond these limits cannot be measured:

• Underflow: Values  -25mV

• Overflow: Values > 2425mV

The sample period is adjustable from 30s up to 100ms by AT^SRADC

Only during sample time (ts~400µs) the S&H Switch is closed.

Figure 30: Analog-to-Digital Converter (ADC)

Restrictions during SLEEP Mode

During SLEEP mode the ADC is shut down temporarily (by default). Please make sure that

during SLEEP mode shutdown the ADCx_IN input voltage does not exceed ±0.3V. The input

current (reverse feeding) may reach 3mA! If SLEEP mode is activated there are three

protection possibilities:

1. Use the RC combination as shown in

Figure 30 for current limitation.

Advantages: Lowest current consumption at SLEEP mode, small component count, high

input resistance

Disadvantages: Lower input resistance at SLEEP mode (100k only).

2. Use the AT^SNFM=,1 command to enable the ADC supply continuously.

Advantages: No additional component components needed.

Disadvantages: Higher current consumption in SLEEP mode (about 2mA).

3. Detect presence of VMIC-voltage. If VMIC is off, make sure that ADCx_IN input voltage

does not exceed ±0.3V

Advantages: Lowest current, high input resistance.

Disadvantages: Effort for SLEEP mode (VMIC) detection.

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