Rev. 1.50
44
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Rev. 1.50
45
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HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
LXT Oscillator C1 and C2 Values
Crystal Frequency
C1
C2
3�.�6�kHz
10pF
10pF
Note
: 1. C1 and C� val�es are for ��idance only.
�. R
P
=5M
Ω
~10M
Ω
is recommended.
32.768kHz Crystal Recommended Capacitor Values
LXT Oscillator Low Power Function
The LXT oscillator can function in one of two modes, the Quick Start Mode and the Low Power
Mode. The mode selection is executed using the LXTLP bit in the TBC register.
LXTLP
LXT Operating Mode
0
Q�ick Start
1
Low-Power
After power on, the LXTLP bit will be automatically cleared to zero ensuring that the LXT oscillator
is in the Quick Start operating mode. In the Quick Start Mode the LXT oscillator will power up
and stabilise quickly. However, after the LXT oscillator has fully powered up it can be placed
into the Low-power mode by setting the LXTLP bit high. The oscillator will continue to run but
with reduced current consumption, as the higher current consumption is only required during the
LXT oscillator start-up. In power sensitive applications, such as battery applications, where power
consumption must be kept to a minimum, it is therefore recommended that the application program
sets the LXTLP bit high about 2 seconds after power-on. It should be noted that, no matter what
condition the LXTLP bit is set to, the LXT oscillator will always function normally and the only
difference is that it will take more time to start up if in the Low-power mode.
Internal 32kHz Oscillator – LIRC
The Internal 32kHz System Oscillator is one of the low frequency oscillator choices, which is
selected via configuration option. It is a fully integrated RC oscillator with a typical frequency of
32kHz at 5V, requiring no external components for its implementation. 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. As a result, at a power supply of 5V and at a temperature of
25°C degrees, the fixed oscillation frequency of 32kHz will have a tolerance within 10%.
Supplementary Oscillators
The low speed oscillators, in addition to providing a system clock source are also used to provide
a clock source to two other device functions. These are the Watchdog Timer and the Time Base
Interrupts.