Datasheet HT7500 Datasheet (Holtek Semiconductor Inc)

Features

Single-chip CMOS construction

·

Single 1.5V battery operation

·

Measurement range: +32.0~+42.0°C

·

(+90.0~+108.0°F)
Measurement accuracy: ±0.1°C(±0.2°F)
Resolution: 0.1°C (0.1°F)
Bonding option for Centigrade/Fahrenheit

·

measurement

General Description

The HT7500 is a CMOS digital clinical ther
mometer IC for measuring body temperature in
Centigrade (°C) or Fahrenheit (°F) mode by its
bonding option. It also provides alarm and auto

Block Diagram

HT7500

Clinical Thermometer

Alarm warning for fever

·

Highest temperature hold

·

Auto power off after 8 min 40 sec

·

One-key input switch for ON/OFF

·

Displays last time measured temperature

·

power off functions. The other electronic com

­ponents are LCD display, thermister, 1.5V bat
tery, ON/OFF switch, buzzer, resistors and
capacitors.

-

-

OSCI

OSCO

TEST2

PSW

CLFH

RF

RS

SC

VDD

VSS

S ystem

OSC

C ontrol

Circuit

Sensor

OSC

TV

TEST1

C ounter and

C om parator

Pulse

G enerator

Pulse
Table

TIM

TS 816

1 August 8, 2000

TIM ER

Voltage
D oubler

C ounter ,

C om parator and

Latch

LCD Driver

LOW C
BZ1
BZ2

C 512
CAP
VEE

COM 1~3
SA1~SD1

HT7500

Pad Assignment

* The IC substrate should be connected to VDD in the PCB layout artwork.

L O W C

VSS

VDD

PSW

SC

RF

RS

TS 816

33

1

2

3

4

5

6

7

8

10

9

TEST2

CLFH

OSCI

OSCO

Chip size: 129 ´ 120 (mil)

TEST1

TIM

32

31

12

BZ1

C 512

CAP

VEE

SC3

TV

29

30

(0 ,0 )

14

13

BZ2

COM 1

SD1

25

26

271128

24

SC2

23

SC1

22

SB3

21

SB2

20

SB1

19

SA3

18

SA2

17

SA1

15

COM 2

2

16

COM 3

Pad Coordinates Unit: mil

Pin No. X Y Pin No. X Y

1
2
3
4
5
6
7
8

9
10
11
12
13

-58.61

-58.61

-58.61 -1.49

-58.61 -13.30

-58.61 -20.95

-58.61 -33.02

-58.61 -40.08

-57.25 -53.63

-50.62 -53.63

-43.99 -53.63

-37.36 -53.63

-15.64 -53.34

-3.19 -53.34

14 7.44
15 26.05
16 58.48
17 58.82

18.57 18 58.82 0.51

6.16 19 58.82 8.24
20 58.82 15.90
21 58.82 23.63
22 58.82 31.28
23 58.82 39.01
24 58.82 46.67
25 46.24 54.06
26 38.59 54.06
27 31.96 54.06
28 24.82 54.06
29 7.39 54.06

-52.66

-52.66

-48.75

30
31
32
33

-0.43

-14.28

-23.63

-42.33

53.29

53.29

53.29

53.29

-7.14

2 August 8, 2000

HT7500

Pad Description

Pad No. Pad Name I/O Function

1 LOWC B For the supply voltage detector, open the pin when not in use.

2 VSS I Power supply GND

3 SC B Common point, NMOS open drain

4 RF O Connect reference resistor, PMOS open drain

5 RS O Connect sensor resistor, PMOS open drain

6 VDD

7 PSW I Pull-low input pin, push switch to turn power on or off

8 TEST2 I

9 CLFH I

10 OSCI I For system oscillator in

11 OSCO O For system oscillator out

12 BZ1 O Buzzer output 1

13 BZ2 O Buzzer output 2

14~16 COM1~COM3 O LCD backplane drive, 3-level voltage out

17~19 SA1~SA3 O LCD segment drive

20~22 SB1~SB3 O LCD segment drive

23~25 SC1~SC3 O LCD segment drive

26 SD1 O LCD segment drive

27 VEE O

28 CAP O For negative voltage, NMOS output

29 C512 O For negative voltage, inverter output

30 TV B Test pin for IC

31 TEST1 I Test pin for IC

32 TIM

33 TS816 I Test pin for IC

Positive power supply

¾

Pull-low test pin, for production test, floating LCD displays
the real time value, when connected to VDD, LCD displays
the highest value.

Floating for °C, connect to VDD for °F

Generate negative voltage (-1.5V)

I Test pin for IC

3 August 8, 2000

Absolute Maximum Ratings

Supply voltage ...................................0V to 2.0V

Operation Temperature ...........-2.0°Cto+75°C

HT7500

Input voltage .................V

Storage Temperature ..............-55°C to +125°C

-0.5V to VDD+0.5V

SS

Note: These are stress ratings only. Stresses exceeding the range specified under ²Absolute Maxi

mum Ratings² 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 expo
sure to extreme conditions may affect device reliability.

Electrical Characteristics

Ta=25°C

Test Conditions

Symbol Parameter

V

DD

I

DD

I

STB

f

OSC

R°C

R°F

Operating Voltage

Operating Current 1.5V No load

Standby Current 1.5V

Oscillating Frequency 1.5V

Temperature Measurement
Accuracy at Range 35°C~39°C

Temperature Measurement
Accuracy at Range 95°F~102°F

DD

Conditions

V

¾¾

¾¾¾

=820kW

R

OSC

¾¾-0.1 ¾

¾¾-0.2 ¾

Min. Typ. Max. Unit

1.3 1.5 1.65 V

¾

60 100

1.0

mA

mA

25.6 32 38.4 kHz

0.1

0.2

°C

°F

LCD Electrode Pattern

H1 F1

H1

E1

A1

B1

G1

C1

D1

A2 A3

F2 F3

E2 E3

B2 B3

G2 G3

C2 C3

D2 D3

H2

A4

B4

C4

H3

-

-

SA1 SA2 SA3 SB1 SB2 SB3 SC1 SC2 SC3 SD1

COM1 F1 A1 B1 F2 A2 B2 F3 A3 B3 A4

COM2 E1 G1 C1 E2 G2 C2 E3 G3 C3 B4

COM3 H1 D1

¾¾

D2 H2

¾

D3 H3 C4

Note: 1/3 duty, 1/2 bias (LCD uses 3V)

4 August 8, 2000

Function Description

·

Power sw: push switch to power on or power
off.

·

When power on: push the switch, then it will
generate a ²beep² sound for 0.125 sec.

a. First displays all the segments on for 2 sec.

b. After a. as described above, then shows the

last time measured temperature for 2 sec.

c. After b., shows L °Cor °F for 0.75 sec.

d. After c., displays the measured temperature,

then °Cor°F mark will flash at a speed of 1Hz.

e. If the temperature is < 32°C (or 90°F), the

display shows L °C (or °F).

f. If the temperature ³ 42°C (or 108°F the

display shows H °C (or °F).

g. The display always shows the higher

temperature during the temperature
measurement.

h. If the measured temperature does not

change for more than 16 sec., the measure­ment is over and the °C (or °F) mark flash

stops.

i. When measurement is over, if the

temperature > 37.5°C (or 99.5°F) the
buzzer alarms ²beep-beep-beep-beep­beep-beep-² for 4 sec, as follows:

BI BI

0.125S 0.125S 0.125S 0.125SBI0.125S 0.125S 0.375S

HT7500

j. It will automatically turn the power off when

measurement is over for 8 min 40 sec.

k. When measurement is over, but if the

temperature rises within 8 min 40 sec, the

°C (or °F) mark will flash again (repeat
from step 2-d), and starts to count 8 min
40 sec again.

l. When beep sound is on for 4 sec, the

temperature is not measured.

·

When power off: the standby current £ 1mA.

·

The frequency of the buzzer is 5.3kHz

·

Bonding option °Cor°F

·

Measurement to 0.1 degree in either °Cor°F

·

Sensor use 503ET

·

Reference resistor is the value
(sensor in 37.0°C)

·

When battery voltage is low, the battery mark

Ñ flashes at the speed of 1Hz and the mea
surement may not be accurate. The low volt
age detect: 1.35V ± 0.05V.

·

During the process of mass production, in or­der to adjust the reference resistance (RF), let
test 2 be floating, the measured temperature
will be the actual temperature of the mea­sured environment. It can be up or down, not
always the higher one.

-

-

if the temperature £ 37.5°C (or 99.5°F), the
buzzer alarms ²beep-beep-beep-beep-² for
4 sec, as follows:

BI

0.5S 0.5S

5 August 8, 2000

Flow Chart

HT7500

Power On

Display

L C

D isplay All S egm ent

D isplay Last M easured

Tem perature

D isplay L C

M easure

D isplay the

H ighest Value

Display

N ot C hanged for

O ver 16 sec

Alarm

2 sec

2 sec

0.75 sec

Display

H C

No

C N ot Flash for 4 sec

(C a n 't M e a s u re )

Yes

Tem perature

R ises w ithin

8 m in 40 sec

No

Power Off

6 August 8, 2000

Application Circuits

HT7500

C 512

CAP
VEE

SD1

COM 3

COM 2

COM 1

0.022mF

0.022mF

To LCD

1.5V

Battery

400k

2200~2700pF

R

B uzzer

W

REF

SENSO R

=820k

OSC

W

LOW C
VSS
SC
RF
RS
VDD
PSW
TEST2
CLFH

OSCI

OSCO

BZ1

BZ2

SC1~3

SB1~3

SA1~3

0 6%#

Note: Substrate connect to VDD

VEE, CAP, and C512 are externally connected to capacitors for stabilizing V

EE

BZ1 and BZ2 are connected to an external buzzer to generate sounds.

LOWC is connected to an external resistor for adjusting the detector level of a low voltage de
tector. Open the pin when not in use.

OSCI, OSCO are connected to an external resistor, and form an RC oscillator with a built-in
capacitor for SYSTEM clock (=32kHz)

RS, RF, SC constitute an alternating RC oscillator, which allows one oscillator, namely RS or
RF, active at a time.

REF (reference resistor) is a resistor value equal to 503ET, sensor is value in 37.0 °C or 98.6 °F.

SENSOR is a 503ET thermistor.

(=-1.5V).

-

7 August 8, 2000

HT7500

Holtek Semiconductor Inc. (Headquarters)

No.3 Creation Rd. II, Science-based Industrial Park, Hsinchu, Taiwan, R.O.C.
Tel: [phone]
Fax: [phone]

Holtek Semiconductor Inc. (Taipei Office)

5F, No.576, Sec.7 Chung Hsiao E. Rd., Taipei, Taiwan, R.O.C.
Tel: [phone]
Fax: [phone]
Fax: [phone] (International sales hotline)

Holtek Semiconductor (Hong Kong) Ltd.

RM.711, Tower 2, Cheung Sha Wan Plaza, 833 Cheung Sha Wan Rd., Kowloon, Hong Kong
Tel: [phone]
Fax: [phone]

Copyright Ó 2000 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 pres
ent a risk to human life due to malfunction or otherwise. 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.

8 August 8, 2000

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