L9805 Datasheet, PDF (57/103 Pages) STMicroelectronics – Super Smart Power Motor Driver with 8-BIT MCU, CAN Interface, 16K EPROM, 256Bytes RAM, 128 Bytes EEPROM, 10 Bit ADC, WDG, 2 Timers, 2 PWM Modules, Ful

L9805
5.5.3 Input Selections and Sampling
The input section of the ADC includes the analog
multiplexer and a buffer. The input of the buffer is
permanently connected to the multiplexer output.
The buffer output is fed to the sample and hold cir-
cuit.
The multiplexer is driven with CH1 and CH0 bit
only after ADST is set. Starting from this event, the
sampler follows the selected input signal for 2.5us
and then holds it for the remaining conversion time
(i.e. when the conversion is actually running).
5.5.4 Interrupt Management
If ADIE bit is set in register ADCCSR, an interrupt
is generated when a conversion is completed (i.e.
when COCO is set).
The interrupt request is cleared when any of the
ADC registers is access (either read or write).
Enabling/disabling the interrupt generation while
the conversion is running has no effect on the cur-
rent conversion. ADIE value is latched when
ADST is set and this internal value holds all the
conversion time long.
5.5.5 Temperature Sensing
The AD1 input is internally connected to the output
of a temperature sensing circuit.
The sensor generates a voltage proportional to the
absolute temperature of the die. It works over the
whole temperature range, with a minimum resolu-
tion of 1LSB/°K (5mV/°K) (Figure 33 shows the in-
dicative voltage output of the sensor).
Note The voltage output of the sensor is only relat-
ed to the absolute temperature of the silicon junc-
tions. Junction temperature and ambient tempera-
ture must be related taking in account the power
dissipated by the device and the thermal resist-
ance Rth_je between the silicon and the environ-
ment around the application board.
Figure 33. Temperature Sensor output
V_TEMP
2.5
m ax
2.2
m in
1.9
1.6
1.3
1.0
223
273
323
373
423
473
Temperature (°K)
The output of the sensor is not ratiometric with the
voltage reference for the ADC conversion (VCC).
When calculating the ADC reading error of this sig-
nal the variation of VCC must be accounted. Addi-
tional errors are due to the intrinsic spread of the
sensor characteristic.
5.5.6 Precise Temperature Measurement
To allow a more precise measurement of the tem-
perature a trimming procedure can be adopted (on
request).
The temperature is measured in EWS and two val-
ues are stored in four EEPROM bytes (see memo-
ry map):
T0L,T0H: temperature of the trimming measure-
ment (in Kelvin).
VT0L,VT0H: output value of the ADC correspond-
ing to T0 (in number of LSBs).
The corrected measurement of the temperature in
Kelvin must be accomplished in the following way:
TEMP (in °K) = VTEMP * T0 / VT0
where VTEMP is the output code in LSB of the
ADC corresponding to the measurement.
Example:
If the value stored in EEPROM are:
0C7Ch: 01h ->T0H
0C7Dh: 43h ->T0L
0C7Eh: 01h -> VT0H
0C7Fh: 5Ch -> VT0L
T0 = 0143h = 323K (50 Celsius)
VTo = 015Ch = 348 LSB (conversion of 1.7V, sen-
sor output)
and the sensor output is 2V, converted by the ADC
in code 0110011001 = 019Ah = 410LSB, the tem-
perature of the chip is
TEMP = 019Ah * 0143h / 015Ch = 017Ch
equivalent to:
TEMP = 410 * 323 / 348 = 380 K = 107 °C
Note The sensor circuit may have two kind of er-
ror: one translating its output characteristic up and
down and the other changing its slope. The de-
scribed trimming recovers only the translation er-
rors but can not recover slope error. After trim-
ming, being T_TRIM the trimming temperature, the
specified precision can be achieved in the range
T_TRIM-80, max[T_TRIM+80, 150°C]. Precision is re-
lated to the read temperature in Kelvin.
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