HT46R0664 datasheet(29/92 Pages) HOLTEK

29 / 92 page

Rev. 1.00

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Rev. 1.00

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HT46R0664

Enhanced A/D+LCD 8-Bit OTP MCU

To i nt er na l

ci rc ui ts

In te rn al

O sc illa to r

Ci rc ui t

No te :1 . Rp , C1 a nd C2 a re r e qui re d.

2. A lt hough n ot s ho wn p in s ha ve a

p ar as it ic c apac it an ce o f ar ound 7pF .

In te r nal R C

Os c illa to r

32768 Hz

External LXT Oscillator – LXT

LXT Oscillator C1 and C2 Values

Crystal Freq�ency

C�

3�768Hz

8pF

10pF

Note: 1. C1 and C� val�es are for ��idance only.

�. RP=5MΩ~10MΩ is recommended.

A configuration option determines if the XT1/XT2 pins are used for the LXT oscillator or as I/O

pins.

● If the I/O option is selected then the XT1/XT2 pins can be used as normal I/O pins.

● If the “LXT oscillator” is selected then the 32kHz crystal should be connected to the XT1/XT2

pins.

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 CTRL4 register.

LXTLP Bit

LXT Mode

Q�ick Start

Low-power

After power on the LXTLP bit, it 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 be

always function normally, the only difference is that it will take more time to start up if it is in the

Low-power mode.

Internal Low Speed Oscillator – LIRC

The LIRC is a fully self-contained free running on-chip RC oscillator with a typical frequency

of 32kHz at 5V requiring no external components. When the device enters the Idle/Sleep Mode,

the system clock will stop running but the WDT oscillator continues to free-run and to keep the

watchdog active. If “LVR is enabled” or “WDT is enabled” or “fS clock source is LIRC”, LIRC

Oscillator is turn on. On the contrary, LIRC Oscillator is turn off if “LVR is disabled” and “WDT is

disabled” and “fS clock source is LXT or fSYS/4”.

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