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HT16566 1/2 Duty VFD Digital Clock
Features
* VFD display 24 hour clock function * Directly drive VFD panels at 1/2 Duty cycle * 4.194304MHz crystal oscillation * Zero adjust function * Integrated voltage regulator permits wide 4V to 18V
operating voltage range
* Four levels of illumination control function * 30-pin SSOP package
General Description
The HT16566 provides direct drive to VFD panels to implement a 24 hour clock function. Obtaining its time base from a 4.194304MHz crystal oscillation source and in having a wide operating voltage due to its internal voltage regulator, the device also contains a host of other features. These include a choice of adjustment modes, including single push increment or 2Hz fast forward functions. Additional features are provided in the form of Blank control, Zero adjustment and four levels of illumination control.
Block Diagram
VCC VSS V
DD
V
DD
V o lta g e R e g u la to r C ir c u it
VDD
V
DD
H o u r C o u n te r A /C V T im e A d ju s tm e n t
DD
1a,3a 1b,3b 1c,3c 1d,3d 1e,3e 1 f, 3 f 1g,3g 2a,2d,4a 2b,4b 2 c , c o l* 2 c , c o l'* 2e,4e 2 f, 4 c
ZA V
M in u te C o u n te r
DD
Segm ent D ecoder
S e g m e n t O u tp u t D r iv e r
HS V
DD
S e c o n d C o u n te r
MS BLANK TEST C o lo n F re q u e n c y
2g,4g,4d 64Hz
XT O s c illa to r XT D IM 1 B r ig h tn e s s A d ju s tm e n t D IM 2 G r id D ecoder F r e q u e n c y D r iv e r C ir c u it G r id O u tp u t D r iv e r
GR1
GR2
Note: * col indicates a blink colon and col indicates a continuous light colon. Rev. 1.00 1 March 28, 2007
HT16566
Pin Assignment
GR2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 VCC VDD 64Hz TEST BLANK D IM 1 D IM 2 XT XT VSS A /C ZA HS MS 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 GR1 2a,2d,4a 2b,4b 2 f, 4 c 2 c , c o l* 2 c , c o l'* 2e,4e 2g,4g,4d 1d,3d 1e,3e 1c,3c 1g,3g 1 f, 3 f 1 b ,3 b 1a,3a
H T16566 3 0 S S O P -A
Note: * col indicates a blink colon and col indicates a continuous light colon.
Pin Description
Pin Name VCC VDD VSS DIM1 DIM2 A/C I/O 3/4 O 3/4 I I I High voltage power supply pin. Built-in regulator voltage output pin for the device internal circuits. Ground pin. Illumination level control pins. Internally connected to pull-down resistors. When the A/C pin is low, the internal circuits are reset. The reset pulse width should be more than 2ms. Internally connected to a pull-high resistor. Zero Adjustment pin. Internally connected to a pull-high resistor. Hour Adjustment pin. Internally connected to a pull-high resistor. Minute Adjustment pin. Internally connected to a pull-high resistor. When low the Blank input pin will extinguish the display. Internally connected to a pull-down resistor. Crystal oscillator pin XT TEST 64Hz GR1 GR2 1a,3a ~ 2b,4b,4c I I O O Grid output pins for 1/2 duty VFD O O Segment output pins for 1/2 duty VFD IC test pin - should be left open or kept at a low level 64Hz signal output pin for oscillation frequency adjustment Description
ZA HS MS BLANK XT
I I I I O
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HT16566
Approximate Internal Connections
D IM 1 , D IM 2 , T E S T , B L A N K A /C , Z A , H S , M S V V V
CC
64Hz V
DD
CC
DD
V
DD
VSS VSS
VSS
1a,3a ~ 1g,3g;2a,2d ~ 2g; G R 1,G R 2
XT,XT
V
CC
XT ( O s c illa to r O u tp u t)
XT ( O s c illa to r In p u t) VSS
VSS
Absolute Maximum Ratings
Logic Supply Voltage .................VSS-0.3V to VSS+6.5V High Input Voltage .....................VSS-0.3V to VCC+0.3V Logic Input Voltage ....................VSS-0.3V to VDD+0.3V Driver Output Voltage..........................VSS-0.3V to VCC Driver Output Current (Grid Driver) ......-7mA to +20mA Operating Temperature.........................-40C to +85C Note: These are stress ratings only. Stresses exceeding the range specified under Absolute Maximum Ratings may cause substantial damage to the device. Functional operation of this device at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability. Driver Supply Voltage .................VSS-0.3V to VSS+20V High Output Voltage ..................VSS-0.3V to VCC+0.3V Logic Output Voltage .................VSS-0.3V to VDD+0.3V Driver Output Current (Segment Driver) -10mA to +2mA Storage Temperature ..........................-55C to +150C
Recommended Operating Conditions
Symbol VCC fOSC tOP Parameter Power Supply Voltage Oscillation Frequency Operating Temperature Min. 4 3/4 -40 Typ. 3/4 4.194304 3/4 Max. 18 3/4 85 Unit V MHz C
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HT16566
D.C. Characteristics
Test Conditions Symbol VIH VIL IIL1 IIH1 IIL2 IIH2 IIL3 IOL IOH ISOL ISOH IGOL IGOH Parameter VDD High Input Voltage Low Input Voltage Low-level Input Current Hi-level Input Current Low-level Input Current Hi-level Input Current Low-level Input Current Low-level Output current Hi-level Output current Driver Output Low Voltage (All Segment outputs) Driver Output High Voltage (All Segment outputs) Driver Output Low Voltage (Grid1,Grid2) Driver Output High Voltage (Grid1,Grid2) Dynamic Current Consumption 3/4 3/4 18V 18V Conditions VCC= 8V to 18V VCC= 8V to 18V Dim1, Dim2, BLANK, Test pins low Dim1, Dim2, BLANK, Test pins high 3.6 3/4 -1 50 -3 -3 -200 100 3/4 15 3/4 15 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 1 3/4 200 3 3 -50 3/4 -100 3/4 -1.0 3/4 -15 V V mA mA mA mA mA mA mA mA mA mA mA Min. Typ. Max. Unit VCC=12V, VSS=0V, Ta=-40C~85C
18V XT pin low 18V XT pin high 18V A/C, ZA, HS, MS pins low 12V VOL= 0.5V for 64Hz pin 12V VOL= 4.0V for 64Hz pin 12V VSOL= 0.7V 12V VSOL= 11.3V 12V VSOL= 0.7V 12V VSOL= 11.3V fOSC= 4.194304MHz, 12V Oscillator external capacitors = 22pF
ICC
1.0
mA
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HT16566
Functional Description
VFD Display Driving The display can directly drive VFD signals dynamically and does so at a 1/2 duty cycle rate. The clock will be displayed in a 24-hour format with the hours ranging from 0 to 23 and minutes from 00 to 59. If the most significant numeral is zero then the display will be extinguished.
* Grid and segment connections
The TEST pin is used during manufacturing for device testing purposes and should not be connected to any external circuitry. Two illumination level set pins, DIM1 and DIM2, are provided to give control over the display brightness level, as shown in the following table. Switch Pin Name Dim1 L Dim2 L L H H f=256Hz, 1/2 duty (50% display) f=256Hz, 1/4 duty (25% display) f=256Hz, 1/8 duty (12.5% display) f=256Hz, 1/16 duty (6.25% display)
A single 7-segment display is shown below showing the illumination pattern for each numeral.
A F G D C E B
Operating mode
7 -S e g m e n ts
H L
As the device is designed for clock applications, four 7-segment displays are required to display the correct time output. The connections for the grids and segments are shown below, however it should be noted that the fourth segment only requires two of its segments to be driven. Additionally it should be noted that the colon can also be illuminated.
GR2 4a 4g 4e 4d d ig it4 4c 4b 3e 3f 3d d ig it3 3a 3g 3c 3b 2e col c o lo n col GR1 2a 2f 2d d ig it2 2g 2c 2b 1e 1f 1d d ig it1 1a 1g 1c 1b
H
Device Functions
* Reset
Although the device is provided with an external reset pin A/C, the device will in fact reset itself when power is applied, eliminating the need for external reset components. The usual provision of an external capacitor is not required as an internal reset capacitor is integrated within the device.
* Internal regulator
An internal regulator function is also integrated within the device providing a stable voltage power supply source for the internal circuits. This allows the device to operate with a wide external power supply ranging from 4V to 18V.
* Chatter removal
Other Pin Functions The external reset pin A/C is used to reset the internal circuits of the device. When this pin is pulled low the device will be reset, when the pin is allowed to go high, via its internal pull-high resistor, then the display will indicate a 0:00 output. The BLANK pin, if pulled low will extinguish the display. Note that during the time when the BLANK pin is low, the HS, MS and ZA pins will be automatically disabled by the device and have no function. The 64Hz pin allows monitoring of the system frequency to allow frequency adjustments to be executed. As the name suggests, this output pin will continuously output a frequency of 64Hz.
The device contains circuits which are connected to input pins HS, MS and ZA to remove chatter of less than 31.25ms.
* Oscillator
The basic time base frequency for this device is determined by an external 4.194304MHz crystal. When an external crystal along with two small external capacitors are connected to the two oscillator XT pins, the internal oscillator circuit will ensure generation of the correct time base signals. The oscillation frequency, although determined by the external crystal frequency, will also be influenced by the external capacitors, the crystal inherent capacitance and the residual capacitance of the external PCB tracks. To ensure accurate frequency generation, the crystal specification should be carefully consulted and the external capacitors and crystal should be placed as close to the device as possible.
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HT16566
Time Adjustment Operation
* Hour/minute adjustment
Both the minutes and hour displays can be adjusted separately or both together in a fast forward format. The hour set pin, HS, and the minutes set pin, MS, are used to make these adjustments. Both of these pins are connected to internal pull-high resistors. Each time one of these lines is pulled low, the respective hour or minute value will increment by one, also if the line is continuously held low then the respective value will increment automatically at a rate of 2Hz. Both values will increment together if both lines are pulled low simultaneously. Note that no carry functions will be implemented when either the hour or minute value overflows.
* Zero adjustment
minute value is presently less than 30 the only the second and minute values will be reset to zero and the hour value remain unchanged. However if the minute value is presently at a value of 30 or higher then when the zero adjustment function is executed, a carry will be implemented and the hour value will be incremented by one. The following table illustrates a few examples of this operation. Zero Adjust Examples Present Time Hr. 1 2 2 2 2 3 Min. 30 00 29 30 59 29 Sec. 00 00 59 00 59 59 After Zero Adjust Hr. 2 2 2 3 3 3 Min. 00 00 00 00 00 00 Sec. 00 00 00 00 00 00
A zero adjust function is also included within the device and is controlled by the ZA pin. This pin is connected to an internal pull-high resistor. Pulling this line low will reset both the internal minutes and seconds value, however the way in which the display is reset depends upon the present value of the display. If the
Application Circuits
V
CC
V
CC
V
CC
V
CC
EF V
CC
SW 7 R1
SW 6
SW 5
VCC 2 c , c o l' 2c,col 2a,2d,4a TEST D IM 1 D IM 2 BLANK 2b,4b 2 f, 4 c 2e,4e 2g,4g,4d 3d,1d 3e,1e 3c,1c 3g,1g 3 f, 1 f 3b,1b 3a,1a A /C ZA HS GR1 GR2 Jum per 1 3 2
F+
F-
2c,col 2a,2d,4a 2b,4b 2 f, 4 c 2e,4e 2g,4g,4d 3d,1d 3e,1e 3c,1c 3g,1g 3 f, 1 f 3b,1b 3a,1a GR1 GR2 1 /2 D u ty VFD Panel
SW 8
XT Y1 4 .1 9 4 3 0 4 M H z XT VDD VSS 64 Hz 2 C1 1
SW 4
SW 3
SW 2
SW 1
MS
C2
Jum per
Note: Capacitor C9 and C10 can adjust the accuracy of frequency Rev. 1.00 6 March 28, 2007
HT16566
Package Information
30-pin SSOP (300mil) Outline Dimensions
30 A
16 B
1 C C' D E
15
G H = F
Symbol A B C C D E F G H a
Dimensions in mil Min. 291 196 9 390 65 3/4 2 22 4 0 Nom. 3/4 3/4 3/4 3/4 3/4 26 3/4 3/4 3/4 3/4 Max. 323 220 15 413 73 3/4 3/4 37 8 8
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Preliminary
HT16566
Holtek Semiconductor Inc. (Headquarters) No.3, Creation Rd. II, Science Park, Hsinchu, Taiwan Tel: 886-3-563-1999 Fax: 886-3-563-1189 http://www.holtek.com.tw Holtek Semiconductor Inc. (Taipei Sales Office) 4F-2, No. 3-2, YuanQu St., Nankang Software Park, Taipei 115, Taiwan Tel: 886-2-2655-7070 Fax: 886-2-2655-7373 Fax: 886-2-2655-7383 (International sales hotline) Holtek Semiconductor Inc. (Shanghai Sales Office) 7th Floor, Building 2, No.889, Yi Shan Rd., Shanghai, China 200233 Tel: 86-21-6485-5560 Fax: 86-21-6485-0313 http://www.holtek.com.cn Holtek Semiconductor Inc. (Shenzhen Sales Office) 5/F, Unit A, Productivity Building, Cross of Science M 3rd Road and Gaoxin M 2nd Road, Science Park, Nanshan District, Shenzhen, China 518057 Tel: 86-755-8616-9908, 86-755-8616-9308 Fax: 86-755-8616-9722 Holtek Semiconductor Inc. (Beijing Sales Office) Suite 1721, Jinyu Tower, A129 West Xuan Wu Men Street, Xicheng District, Beijing, China 100031 Tel: 86-10-6641-0030, 86-10-6641-7751, 86-10-6641-7752 Fax: 86-10-6641-0125 Holtek Semiconductor Inc. (Chengdu Sales Office) 709, Building 3, Champagne Plaza, No.97 Dongda Street, Chengdu, Sichuan, China 610016 Tel: 86-28-6653-6590 Fax: 86-28-6653-6591 Holtek Semiconductor (USA), Inc. (North America Sales Office) 46729 Fremont Blvd., Fremont, CA 94538 Tel: 1-510-252-9880 Fax: 1-510-252-9885 http://www.holtek.com
Copyright O 2007 by HOLTEK SEMICONDUCTOR INC. The information appearing in this Data Sheet is believed to be accurate at the time of publication. However, Holtek assumes no responsibility arising from the use of the specifications described. The applications mentioned herein are used solely for the purpose of illustration and Holtek makes no warranty or representation that such applications will be suitable without further modification, nor recommends the use of its products for application that may present a risk to human life due to malfunction or otherwise. Holteks products are not authorized for use as critical components in life support devices or systems. Holtek reserves the right to alter its products without prior notification. For the most up-to-date information, please visit our web site at http://www.holtek.com.tw.
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March 28, 2007

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