AMC7834 Datasheet, PDF (30/93 Pages) Texas Instruments – AMC7834 12-Bit Integrated Power-Amplifier Monitor and Control System with Temperature, Current and Voltage Supervision Capabilities

AMC7834
SLAS972B – NOVEMBER 2014 – REVISED MARCH 2016
www.ti.com
The DACs can be forced to enter clamp mode by the alarm events controlling the ALARMOUT pin. The
ALARMOUT clamp register (address 0x1A) selects the DAC or DAC pairs that enter clamp mode when the
ALARMOUT pin goes active. Restoring the ALARMOUT pin does not automatically return the DAC or DAC pairs
back to normal operation.
7.3.2 Analog-to-Digital Converter (ADC)
The AMC7834 device features a monitoring system centered on a 12-bit successive approximation register
(SAR) ADC fronted by a 15-channel multiplexer and an on-chip track-and-hold circuit. The monitoring system is
capable of sensing up to 4 external inputs (0 to 2.5 V range), 4 internal inputs (bipolar DAC monitoring), 4
current-sense amplifier inputs, 2 remote temperature sensors, and an internal analog-temperature sensor.
The ADC can operate from either an external 2.5 V reference or the device internal reference (V_ref). The ADC
input range is 0 V to V_ref. All ADC inputs are internally mapped to this range. The ADC timing signals are derived
from an on-chip temperature-compensated oscillator. The conversion results can be accessed through the device
serial interface.
7.3.2.1 External Analog Inputs
The AMC7834 has 4 analog inputs for external voltage sensing (ADC1 through ADC4). Figure 47 shows the
equivalent circuit for each external analog input pin. The two diodes, D1 and D2, provide electrostatic discharge
(ESD) protection for the individual analog pins. Diode D1 turns on when any of the inputs is greater than AV_DD +
0.3 V. Similarly diode D2 turns on when any of the inputs is less than AGND – 0.3 V. The switch is open while
the ADC is in the READY state.
AVDD
ADCx
D1
S(W)
RS
C(SAMPLE)
D2
S(W) is closed during acquisition.
S(W) is open during conversion.
Figure 47. ADC External Inputs Equivalent Circuit
The analog input range for inputs ADC1 through ADC4 is 0 V to V_ref and the LSB (least-significant bit) size is
given by V_ref / 4096. The analog input conversion values are stored in straight binary format in the ADC-External
Data registers (address 0x24 through 0x27). The input voltage is calculated using Equation 2.
V_IN
CODE u V_ref
4096
(2)
To achieve specified performance it is recommended to drive each analog input pin with a low impedance
source. In applications where the signal source has high impedance, analog input must be buffered.
7.3.2.2 Internal Bipolar DAC Monitoring Inputs
The AMC7834 has 4 internal inputs used for monitoring the bipolar DAC outputs (ADCINT1 through ADCINT4).
The internal monitoring inputs are particularly useful when the AMC7834 operates in closed-loop mode as the
bipolar DAC outputs are autonomously updated by the closed-loop controllers. Continuous monitoring of the
bipolar DAC outputs helps in detecting closed-loop controller issues.
The input range for the internal monitoring channels is -2 × V_ref to V_ref and the LSB size is given by 3 × V_ref/4096.
The monitored signals are scaled through a resistor divider so that they map to the native input range of the ADC
(0 to 2 × V_ref).
The internal monitoring inputs conversion values are stored in straight binary format in the ADC-Internal Data
registers (address 0x20 through 0x23). The monitored bipolar DAC output voltage is calcualted by Equation 3.
V_ADCINT
V_ref
3
§
¨©
V_ref
u CODE
4096
·
V_{ref ¸¹}
(3)
30
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