User Manual

Apollo3 Blue Datasheet

DS-A3-0p9p1 Page 523 of 909 2019 Ambiq Micro, Inc.

12. Clock Generator and Real Time Clock Module

Figure 63. Block diagram for the Clock Generator and Real Time Clock Module

12.1 Clock Generator

12.1.1 Functional Overview

A high-level view of the Clock Generator Module, which supplies all clocks required by the Apollo3 Blue

MCU, is shown in Figure 63. These clocks are derived from one of three fundamental clock sources: a high

precision crystal controlled oscillator (XT), a low power 1 kHz RC oscillator (LFRC) and a high frequency

48/96 MHz oscillator (HFRC).

A clock, CLKOUT, generated from any of the oscillators, may be configured and driven onto an external

pin. CLKOUT also drives the Real Time Clock (RTC) Module and other internal clock nodes.

The Clock Generator automatically controls the enabling of the oscillators, so that they are only powered

up and used when requested by another module. This allows minimal power consumption without complex

XT Chain

LFRC Chain

HFRC Chain

CLKOUT

Core, Flash

100 Hz

Osc

LFRC Osc

HFRC Osc

Calibration

Registers

Module Clocks

Autocal Logic

RTC