FT902Q-R datasheet(51/67 Pages) BRIDGETEK

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FT900

/1/2/3 Revision C Embedded Microcontroller Datasheet

Version 1.0

Document No. BRT_000172 Clearance No.: BRT#087

Application Information

6.1

Crystal Oscillator

The crystal oscillator operates at a frequency of 12MHz. The oscillator can operate one of two following

configuration.

6.1.1 Crystal oscillator application circuit

FT900

XI/CLKIN

XIO

XTAL

12MHz

Figure 6-1 - Crystal oscillator connection

Feedback resistance is integrated on chip; only a crystal and capacitors CL need to be connected

externally. With the proper selection of crystal, the oscillator circuit can generate better quality signals for

FT900/1/2/3. Parameter CL is typically 27pF but should be checked with the crystal manufacturer.

6.1.2 External clock input

FT900

XI/CLKIN

XIO

12MHz

Figure 6-2 - External clock input

The 12MHz input clock signal connects XI/CLKIN to internal oscillator directly. The XIO pin can be left

unconnected.

6.2

RTC Oscillator

In the RTC oscillator circuit Figure 6-3, only a 32.768 KHz crystal and capacitors CRTCL need to be

connected externally. The parameter CRTCL should be checked with the crystal manufacturer.

An external input clock Figure 6-4 can be connected to RTC_XI/RTC_CLKIN if RTC_XIO is left open.

FT902Q-R 数据表(PDF) 51 Page - Bridgetek Pte Ltd.