MAX32600 User’s Guide
System Clock, Timers/Counters, Watchdog Timers and Real Time Clock
10.1 System Clock
10.1.1.1
External High-Frequency Crystal Oscillator
The
MAX32600
includes a high-frequency crystal oscillator circuit designed to operate with an external crystal. Fundamental mode crystals can be used with the
oscillator circuit up to a frequency of 24MHz. External load capacitors are required depending on the crystal specifications.
An external clock source may also be used by the
MAX32600
in place of a high-frequency crystal. For this configuration, the external clock source is connected to
the part on the HFXIN pin, and the HFXOUT pin is left floating.
10.1.1.2
32kHz Crystal Oscillator
A 32kHz crystal oscillator (with the 32kHz crystal connected between the 32KIN and 32KOUT pins) is used to generate the 32kHz clock that is used by the
module.
An external clock source may also be used by the
MAX32600
in place of a 32kHz crystal. For this configuration, the external clock source is connected to the part
on the 32KIN pin.
10.1.1.3
48MHz USB Clock PLL
The phase locked loop (PLL) clock generation circuit is used to generate a 48MHz clock which is required for proper operation of the
. If the
USB interface will not be used, use of the PLL is optional.
The PLL generates a 48MHz clock using a clock multiplier circuit of either 2X, 4X, or 6X. The PLL supports 2X mode for use with a 24MHz external crystal, 4X mode
for use with a 12MHz external crystal, and 6X mode for use with an 8MHz external crystal. Additionally, the PLL output can be used as a system clock source (after
dividing it by two) with a 24MHz frequency.
10.1.1.4
48MHz Internal 24MHz Trimmed Relaxation Oscillator
An internal trimmed relaxation oscillator generates a 24MHz (
±
1%) clock that can be used as a system clock source. If calibrated to the 32kHz crystal, this can be
used as the input to the PLL to generate the USB clock.
10.1.1.5
Cryptographic Internal Oscillator
The
MAX32600
provides a dedicated on-chip oscillator used to supply a separate isolated clock to reduce opportunities of clock interference attacks. Specifically,
timing-based analysis and fault injection attacks on sensitive functions of the device are mitigated with this feature. Vulnerabilities protected by the isolated crypto-
graphic internal oscillator include timing-based and security functions such as the
and the
Modular Arithmetic Accelerator (MAA)
among
others.
Effectively decoupling these sensitive functions from the main system clock allows encryption and decryption operations to take a consistent amount of time regardless
Rev.1.3 April 2015
Maxim Integrated
Page 500