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Maxim > Design Support > Technical Documents > Application Notes > Measurement Circuits > APP 4318
Keywords: adc, a/d, a-d, ADCs, analog to digital converter, 12-bit, 8-bit, 2-wire, I2C, High Speed I2C,
HS-I2C, Hs-I2C, 1.7MHz, serial interface, microcontroller, microcontrollers, micros, assembly,MAXQ,
MAXQ2000
APPLICATION NOTE 4318
High-Speed I²C for the MAX1239 ADC Using the
MAXQ2000 Microcontroller
By: Ted Salazar, Applications Engineering Manager
Sep 26, 2008
Abstract: This application note provides a much-needed working high-speed I²C example. The
application note shows an application circuit and provides all the firmware required to interface the
MAXQ2000 microcontroller (MAXQ20 core) to the MAX1239 for a conversion rate of 91ksps. The
example firmware was developed using the MAX-IDE Version 1.0.
MAX1239 Overview
The MAX1239 is a 12-channel, 12-bit, low-power ADC featuring a 1.7MHz high-speed I²C-compatible
serial interface. The MAX1239 supports both Fast/Standard mode (FS mode at 400kHz) and High-Speed
mode (HS mode at 1.7MHz) with conversion rates up to 94.4ksps. HS mode is required to achieve
conversion rates from 26ksps to 94.4ksps. External clock mode is required for conversion rates from
40ksps to 94.4ksps.
Hardware Overview
A simplified system block diagram is shown in Figure 1. The application circuit utilizes two evaluation
(EV) kits: the MAX1238EVKIT with an installed MAX1239 (instead of a MAX1238), and a MAXQ2000-
KIT. The MAX1239 was selected because of the digital-logic voltage range. The MAXQ2000
microcontroller's general-purpose input/output (GPIO) ports only accept up to +3.3V; using level
translators with high-speed I²C would have made the circuit overly complicated. The MAXQ2000 is not
present on the MAX1238 EV kit board, so it was added to the system by connecting SCL, SDA, and
GND on both boards. In addition, it is very important to apply +3.3V (instead of +5V) to V
DD
on the
MAX1238 EV kit board. Order a free sample of the MAX1239EEE or MAX1239EEE+ and solder it onto
the MAX1238 EV kit. The modified MAX1238 EV kit schematic is shown in Figure 2.
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