Application Circuits

Note: The resistance and capacitance for the reset circuit should be designed to ensure that VDD is stable and

remains in a valid range of the operating voltage before bringing RES high.

²*² Make the length of the wiring, which is connected to the RES pin as short as possible, to avoid noise

interference.

The following table shows the C1, C2 and R1 values corresponding to the different crystal values. (For refer-

ence only)

Crystal or Resonator

C1, C2

R1

8MHz Crystal & Resonator

35pF

3.9k

W

4MHz Crystal

10pF

10k

W

4MHz Resonator

10pF

12k

W

3.58MHz Crystal

10pF

12k

W

3.58MHz Resonator

10pF

12k

W

2MHz Crystal & Resonator

35pF

12k

W

1MHz Crystal

68pF

18k

W

480kHz Resonator

300pF

10k

W

455kHz Resonator

300pF

10k

W

429kHz Resonator

300pF

10k

W

400kHz Resonator

300pF

10k

W

The function of the resistor R1 is to ensure that the oscillator will switch off should low voltage condi-

tions occur. Such a low voltage, as mentioned here, is one which is less than the lowest value of the

MCU operating voltage. Note however that if the LVR is enabled then R1 can be removed.

HT48R01/HT48R02/HT48R03

Rev. 1.00

21

December 20, 2006

H T 4 8 R 0 1 / H T 4 8 R 0 2 / H T 4 8 R 0 3

O S C 1

O S C 2

C r y s t a l S y s t e m O s c i l l a t o r

F o r C 1 , C 2 a n d R 1 v a l u e s ,

s e e t a b l e b e l o w

R 1

C 1

C 2

R C S y s t e m O s c i l l a t o r

O S C 1

P A 5

4 7 0 p F

O S C C i r c u i t

R E S / P A 7

0 . 1 m F *

1 0 0 k W

V D D

V S S

0 . 1 m F

0 . 0 1 m F *

1 0 k W

O S C 1

O S C 2

O S C

C i r c u i t

S e e R i g h t S i d e

P A 0 / B Z

P A 1 / B Z

P A 2 / T M R 0

P A 3 / I N T

P A 4 / T M R 1

I n t e r n a l R C O s c i l l a t o r

T w o p i n s a r e c o n f i g u r e d

a s I / O p i n

I n t e r n a l R C O s c i l l a t o r

+ E x t e r n a l R T C O S C

P A 5

P A 6

O S C 1

1 0 p F

3 2 7 6 8 H z

O S C 2