VXI VM4016 user manual Signal Comparison

VXI Technology, Inc.

SIGNAL COMPARISON

Signal comparison between the input signal and a user-defined reference voltage is accomplished by a differential amplifier, an 8-bit Digital to Analog Converter or DAC and a voltage comparator (see Figure 5-2). The DAC, U8, is loaded by the control FPGA, U3, and provides the reference voltage TRIGLEV1.

				100K
				10K	K9
				10pf
(FROM FRONT	-CH1	100K		-
					6K
				U17A
PANEL CONNECTOR)		100K
						2K
	+CH1			+
VMIP BUS				100K
				10K	K9
									VCC
							BUFCH1	-	4.7K
									4.7K
	CONTROL
				DACDATA	D A C	TRIGLEV1	1K		U13A
	FPGA
				DACLOAD#				+
				DACCLK
					U8				470K
	U3								COMPCH1
	CONTROL
Address
0-5, 29	CONTROL
	BUFFER
	U1
Data 0-15	DATA		Data
	BUFFER
DOE*
	U4
				FIGURE 5-2: SIGNAL COMPARISON

The command to specify the reference voltage is received in the data and command buffers and subsequently transferred to the control FPGA at U3. U3 then converts the parallel data to an 8-bit serial data word DACDATA and synchs the output of this word to the 10 MHz gated clock DACCLK. Signal DACLOAD1, for Channel 1, goes high providing the control necessary to shift the serial data into DAC 1. The output TRIGLEV1 of the U8, is used by the comparator U13A as the reference.

90 VM4016 Theory of Operation