MXB7846EVC16 Maxim Integrated, MXB7846EVC16 Datasheet - Page 3

• Manufacturer Part Number: MXB7846EVC16
• Description: Data Conversion IC Development Tools MXB7846C16 Eval Kit
• Manufacturer: Maxim Integrated
• Type: Data Acquisitionsr
• Series: MXB7846r

Specifications of MXB7846EVC16

• Product: Evaluation Kits
• Tool Is For Evaluation Of: MXB7846
• Interface Type: 4-Wire
• Operating Supply Voltage: 7 V to 20 V
• Description/function: MXB7846 evaluation system (EV system) is a complete touch-screen controller data-acquisition system consisting of a MXB7846 evaluation kit (EV kit) and a Maxim 68HC16MODULE-DIP microcontroller (æC) module
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Factory Pack Quantity: 1

A high-impedance source can require a longer acquisi-
tion time for accurate measurement. From the evalua-
tion software’s Low Level tab, set QSPI clock to a suf-
ficiently slow serial clock speed. The minimum clock
rate the 68HC16 module supports is 33kHz, which cor-
responds to an acquisition time of 91µs.
The MXB7846 (U1) is an industry-standard, 4-wire
touch-screen controller. Resistors R2–R7 and capaci-
tors C6–C11 are reserved for optional user-supplied,
single-pole, low-pass, anti-aliasing filters. C3 bypasses
the ADC’s voltage reference. When plugged into the
Figure 1. MXB7846 Touch-Screen Controller EV Kit—Measurement Tab
NOTE: THE EVALUATION SOFTWARE TRACKS THE TOUCH SCREEN IN THE RIGHT HALF OF THE MAIN WINDOW.
THE MEASUREMENT TAB TRACKS TOUCH-SCREEN INPUT, DEVICE TEMPERATURE, AND AUXILIARY INPUTS.
MXB7846 Evaluation Kit/Evaluation System
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Increasing Acquisition Time
Detailed Description
of Hardware
68HC16MODULE, the MAX1615 (U5) provides +3V
power to the MXB7846, and the MAX1840 level shifters
(U3 and U4) translate the 68HC16MODULE’s +5V logic
signals to +3V logic. See Figure 7, MXB7846 EV Kit
Schematic, and refer to the MXB7846 data sheet.
For prototyping purposes, a 4-wire resistive touch
screen can be simulated using two variable resistors
connected by a resistor and a switch. Variable resistor
X, connected between X+ and X-, should be approxi-
mately 100Ω to 500Ω. Variable resistor Y, connected
between Y+ and Y-, should be approximately 100Ω to
500Ω. Connect the center wipers of the two variable
resistors using a fixed resistor of approximately 300Ω,
simulating the touch resistance (Figure 6).
Touch-Screen Equivalent Circuit
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