Clock Gen 3 Click Board™

Product Code: MIKROE-4171

How Does The Clock Gen 3 Click Board™ Work? The Clock Gen 3 Click Board™ uses the LTC6904 IC, 1kHz to 68MHz Serial Port Programmable Oscillator from Linear Technology. The LTC6904 is a low power self-contained digital frequency source providing a precision frequency from 1KHz to 68MHz, which is set by the I2C interface operaing up to 3.4 Mbps. This Click board™ features on-board I2C address jumpers, pull-up resistors, a power supply bypass capacitor, and a power LED. The maximum frequency error is 1.1% or 1.6% when operating with a flexible power supply voltage range from 2.7V to 5V, which makes it suitable for 3.3V and 5V MCUs. In most frequency ranges, the output of the Clock Gen 3 Click Board™ is generated as a division of the higher internal clock frequency. This helps to minimize jitter and subharmonics at the output of the device. In the highest frequency ranges, the division ratio is reduced, which will result in a greater cycle-to-cycle jitter as well as spurs at the internal sampling frequency.

Because the internal control loop runs at 1MHz to 2MHz without regard to the output frequency, output spurs separated from the set frequency by 1MHz to 2MHz may be observed. These spurs are characteristically more than 30dB below the level of the set frequency. The LTC6904 communicates with the MCU using the standard I2C 2-wire interface. The two bus lines, SDA and SCL, must be HIGH when the bus is not in use. If the I2C interface is not driven with a standard I2C compatible device, care must be taken to ensure that the SDA line is released during the ACK cycle to prevent bus contention. The LTC6904 can respond to one of two 7-bit addresses. The first 6 bits (MSBs) have been factory programmed to 001011. The address pin, ADR (Pin 4) is programmed by the user and determines the LSB of the slave address and it can be selected by an onboard SMD jumper labeled as ADD SEL allowing selection of the slave address LSB. The Clock Gen 3 Click Board™ can be supplied and interfaced with both 3.3V and 5V without the need for any external components. The onboard SMD jumper labeled as VCC SEL allows voltage selection for interfacing with both 3.3V and 5V microcontrollers. More information about the LTC6904 can be found in the attached datasheet. However, this Click board™ comes equipped with a library that contains easy to use functions and an example that may be used as a reference for development. SPECIFICATIONS Type Clock generator Applications Can be used as a microcontroller clock source, clock source for a switched capacitor filter, or general replacement for a DAC/VCO combination. On-board modules LTC6904 Key Features Precision frequency generator from 1KHz to 68MHz, minimal jitter and subharmonics at the output, on-board I2C address jumpers Interface GPIO,I2C Compatibility mikroBUS Click board size M (42.9 x 25.4 mm) Input Voltage 3.3V,5V PINOUT DIAGRAM This table shows how the pinout on the Clock Gen 3 Click Board™ corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns). Notes Pin Pin Notes NC 1 AN PWM 16 NC NC 2 RST INT 15 NC Output Enable OE 3 CS RX 14 NC NC 4 SCK TX 13 NC NC 5 MISO SCL 12 SCL I2C Clock NC 6 MOSI SDA 11 SDA I2C Data Power Supply 3.3V 7 3.3V 5V 10 5V Power Supply Ground GND 8 GND GND 9 GND Ground ONBOARD SETTINGS AND INDICATORS Label Name Default Description LD1 PWR - Power LED Indicator JP1 VCC SEL Right Power Supply Voltage Selection 3V3/5V, left position 3V3, right position 5V JP2 ADDR SEL