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HT7501 Clinical Thermometer
Features
* * *
*
Single-chip CMOS construction Single 1.5V battery operation Measurement range: +32.00C~+43.00C Measurement accuracy: 0.1C Resolution: 0.01C Auto self-test
* * * * *
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
General Description
The HT7501 is a CMOS digital clinical thermometer IC for measuring body temperature from 32.00C~43.00C. It also provides alarm, self-test, auto power off and last time measured temperature functions. The other electronic components are LCD display, thermister, 1.5V battery, ON/OFF switch, buzzer, resistors and capacitors.
Block Diagram
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Pad Assignment
Chip size: 121 x 124 (mil)2 * The IC substrate should be connected to VDD in the PCB layout artwork.
Pad Coordinates
Pad No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 X -54.78 -54.78 -54.78 -54.78 -54.78 -54.78 -54.78 -54.78 -54.78 -54.78 -52.53 -44.46 -37.10 -29.88 -22.82 -5.31 5.40 13.64 Y 54.10 46.45 39.10 31.45 24.10 16.45 9.10 1.45 -5.91 -13.56 -56.53 -56.53 -56.53 -56.53 -56.53 -56.53 -56.53 -56.53
2
Unit: mil
Pad No. 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
X 20.27 54.78 54.78 54.78 54.78 54.78 54.02 54.02 54.02 51.13 44.50 37.87 31.24 18.02 1.95 -17.34 -23.97 -40.97
Y -56.53 -56.53 -49.30 -37.99 -25.58 -1.02 8.50 15.13 27.11 55.85 55.85 55.85 55.85 56.61 56.61 56.61 56.61 56.61
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Pad Description
Pad No.
1~3 4~6 7~19 10~12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34~36
Pad Name
SA1~SA3 SB1~SB3 SC1~SC3 SD1~SD3 SE1 VEE CAP C512 TV TEST1 LOWC VSS SC RF RS VDD PSW TEST2 ML FEVL S804KL OSCI OSCO BZ1 BZ2 COM1~COM3
I/O
O O O O O O O O B I B I B O O I I I I I I I O O O O LCD segment drive LCD segment drive LCD segment drive LCD segment drive LCD segment drive
Function
Generate negative voltage (-1.5V) For negative voltage, NMOS output For negative voltage, inverter output Test pin for IC Test pin for IC For the supply voltage detector. Open the pin when not in use. Power supply GND Common point, NMOS open drain Connect reference resistor, PMOS open drain Connect sensor resistor, PMOS open drain Positive power supply Pull low input pin, push switch to turn the power on or off Pull low test pin, for production test, floating LCD displays the real time value, when connected to VDD, LCD displays the highest value. Connect to VDD for memory function, otherwise floating. Floating with fever function, otherwise connect to VDD. Floating buzzer is 4kHz, connect to VDD if buzzer is 8kHz. For system oscillator in For system oscillator out Buzzer output 1 Buzzer output 2 LCD backplane drive, 3-level voltage out
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Absolute Maximum Ratings
Supply voltage.................................... 0V to 2.0V Operation Temperature............. -20C to +75C Input voltage ............... VSS-0.5V to VDD+0.5V Storage Temperature................ -55Cto +125C
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.
Electrical Characteristics
Symbol
VDD IDD ISTB fOSC RC
Ta=25C
Parameter
Operating Voltage Operating Current Standby Current Oscillating Frequency Temperature Measurement Accuracy at Range 35C~39C
Test Conditions VDD
-- 1.5V 1.5V 1.5V --
Min.
1.3 -- -- 25.6 -0.1
Typ.
1.5 60 -- 32 --
Max. Unit
1.65 100 1.0 38.4 0.1 V
A A
Conditions
-- No load -- ROSC=820k --
kHz
C
LCD Electrode Pattern
SA1 COM1 COM2 COM3 F1 E1 H1
SA2 A1 G1 D1
SA3 B1 C1 --
SB1 F2 E2 --
SB2 A2 G2 D2
SB3 B2 C2 H2
SC1 F3 E3 --
SC2 A3 G3 D3
SC3 B3 C3 --
SD1 F4 E4 I4
SD2 A4 G4 D4
SD3 B4 C4 H4
SE1 A5 B5 C5
Note: 1/3 duty, 1/2 bias (LCD uses 3V)
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Functional Description
* Power sw: push switch to turn the power on or
off.
* When power on: push the switch, then it will
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 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 1A. * The frequency of the buzzer is 4kHz or 8kHz
generate a "beep" 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 2.8 sec. c. After b., shows the self-test temperature (37.000.01C ) for 1 sec. The C mark will flash at a speed of 1Hz. d. After c., displays the highest measured temperature, then the C mark will flash at a speed of 1Hz. e. If the temperature is < 32.00C, the display shows Lo C. f. If the temperature is 43.00C, the display shows Hi C. g. The display always shows the higher temperature during the temperature measurement. h. If the measured temperature does not change for more than 8 sec, the measure ment is over and the C mark flash stops. i. When measurement is over, if the temperature > 37.50C the buzzer alarms "beep-beep-beep---beep-beep-beep---" for 4 sec, as follows:
by pin option.
* Fever alarm is pin option. * Measurement to 0.01 degree at C. * Sensor use 503ET. * Reference resistor is the value (sensor in 37.00C) * The low battery and "M" flag cannot display
when the temperature shows Hi or Lo.
* When battery voltage is low, the battery mark
"" flashes at a speed of 1Hz and the measurement may not be accurate. The low voltage detect: 1.35V 0.05V.
* During the process of mass production, in or-
der 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 37.50C, the buzzer alarms "beep-beep-beep-beep-" for 4 sec, as follows:
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Flow Chart
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Application Circuits
Notes: Substrate connect to VDD. VEE, CAP and C512 are externally connected to capacitors for stabilizing VEE (=-1.5V). BZ1 and BZ2 are connected to an external Buzzer for generating sounds. LOWC is connected to an external resistor for adjusting the detector level of a low voltage detector. 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 in 37.00C. SENSOR is a 503ET thermistor.
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