The Analog Comparator (ACMP) compares two voltages and outputs a digital signal indicating which is larger. It has two analog input terminals, IN+ and IN-, and one digital output OUT.

Activation

In order for the ACMP cell to be used in a GreenPAK design, the power up signal (PWR UP) needs to be active (HIGH). It is possible to have each ACMP always on, always off, or switched on dynamically based on a digital signal from the connection matrix.

Parameters

Table 1.

Parameters	ACMP0	ACMP1	ACMP2	ACMP3	ACMP4	ACMP5
IN+ source	PIN6	PIN12	PIN13	PIN15	PIN3	PIN 4
	Buffered PIN6	PGA out	ACMP0 IN+	PIN13	PIN15
	VDD	ACMP0 IN+		ACMP0 IN+	ACMP0 IN+
IN- source	50mV	50mV	50mV	50mV	50mV	50mV
	…	…	…	…	…	…
	1200mV	1200mV	1200mV	1200mV	1200mV	1200mV
	VDD/3	VDD/3	VDD/3	VDD/3	VDD/3	VDD/3
	VDD/4	VDD/4	VDD/4	VDD/4	VDD/4	VDD/4
	PIN10	PIN10	PIN10	PIN10	PIN10	PIN10
	PIN7	PIN7	PIN14	PIN14	PIN14	PIN5
	PIN10 / 2	PIN10 / 2	PIN10 / 2	PIN10 / 2	PIN10 / 2	PIN10 / 2
	PIN7 / 2	PIN7 / 2	PIN14 / 2	PIN14 / 2	PIN14 / 2	PIN5 / 2
	DAC1 out	DAC1 out	DAC1 out	DAC1 out	DAC1 out	DAC1 out
	DAC0 out	DAC0 out	DAC0 out	DAC0 out	DAC0 out	DAC0 out

Hysteresis:

Each ACMP has four selectable hysteresis options 0mV, 25mV, 50mV and 200mV.

• 0mV: will disable the input signal hysteresis;

• 25mV: is a +12.5mV and -12.5mV hysteresis;

• 50mV: is a +0mV and -50mV Hysteresis. For Vref=1V, the trigger points will be 1V and 0.95V. Only applies if Vref is internal;

• 200mV: is a +0mV and -200mV hysteresis. For Vref=1V, the trigger points will be 1V and 0.8V. Only applies if Vref is internal;

Low bandwidth:

Enable/Disable a low pass filter, cutoff frequency << 5kHz, to IN+.

Buffer bandwidth:

Set the maximum frequency that can pass through the input buffer on ‘Buffered PIN6’. Selecting frequencies 5kHz, 20kHz or 50kHz makes current consumption increase significantly. Use ONLY with VDD greater than 2.7V.
While the Buffer Bandwidth parameter is applied to all ACMPs, the effect is only applied on input ‘Buffered PIN6’.

• 1kHz, 5kHz, 20kHz and 50kHz: The current consumption increases significantly at higher bandwidths.

Input 100uA current:

Enable/Disable a 100uA constant current source at the IN+ source

IN+ gain:

The IN+ source has a selectable gain stage of 1X, 0,5X, 0.33X and 0.25X before connection to the analog comparator. A gain stage aside from 1X causes the input impedance to decrease dramatically, see Table below. Use the buffered input ‘Buffered PIN6’ for high input impedance when using the gain divider (0.25X, 0.33X, 0.5X)

Gain	1X	0.5X	0.33X	0.25X
Input Resistance	100 MOhm	1 MOhm	0.75 MOhm	1 MOhm

IN+ source:

Positive Analog input source to ACMP. Input offset for HIGH precision ACMP5 is <1mV, and <5mV for normal ACMP0-4
To use ‘Buffered PIN6’ with ACMP1-5, select select ‘Buffered PIN6’ for the IN+ source to ACMP0. Then select ‘ACMP0 IN+’ for the IN+ source to ACMP1-5.

IN- source:

Negative Analog input source to ACMP. Internal Vref thresholds are optimized near 1000mV.