Rev. 1.10
36
November 04, 2019
Rev. 1.10
37
November 04, 2019
HT45F5Q-3
Battery Charger Flash MCU
HT45F5Q-3
Battery Charger Flash MCU
Prescaler
f
H
High Speed
Oscillator
Low Speed
Oscillator
f
H
/2
f
H
/16
f
H
/64
f
H
/8
f
H
/4
f
H
/32
CKS2~CKS0
f
SYS
f
SUB
f
LIRC
SLEEP
IDLE0
IDLE2
SLEEP
LIRC
HIRC
HIRCEN
f
SUB
System Clock Configurations
Internal High Speed RC Oscillator – HIRC
The internal high speed RC oscillator is a fully integrated system oscillator requiring no external
components. The internal RC oscillator has a fixed frequency of 8MHz. Device trimming during
the manufacturing process and the inclusion of internal frequency compensation circuits are used
to ensure that the influence of the power supply voltage, temperature and process variations on the
oscillation frequency are minimised.
Internal 32kHz Oscillator – LIRC
The Internal 32kHz System Oscillator is the low frequency oscillator
.
It is a fully integrated
RC oscillator with a typical frequency of 32kHz, requiring no external components for its
implementation.
Operating Modes and System Clocks
Present day applications require that their microcontrollers have high performance but often still
demand that they consume as little power as possible, conflicting requirements that are especially
true in battery powered portable applications. The fast clocks required for high performance will
by their nature increase current consumption and of course vice versa, lower speed clocks reduce
current consumption. As Holtek has provided the device with both high and low speed clock sources
and the means to switch between them dynamically, the user can optimise the operation of their
microcontroller to achieve the best performance/power ratio.
System Clocks
The device has many different clock sources for both the CPU and peripheral function operation. By
providing the user with a wide range of clock options using register programming, a clock system
can be configured to obtain maximum application performance.
The main system clock, can come from either a high frequency, f
H
, or low frequency, f
SUB
, source,
and is selected using the CKS2~CKS0 bits in the SCC register. The high speed system clock is
sourced from the HIRC oscillator. The low speed system clock source is sourced from the LIRC
oscillator. The other choice, which is a divided version of the high speed system oscillator has a
range of f
H
/2~f
H
/64.