iC-MQ PROGRAMMABLE 9-BIT
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev D4, Page 16/39
BIAS CURRENT SOURCE AND TEMPERATURE SENSOR CALIBRATION
Bias Current
Example: VTs(T1) is ca. 650 mV, measured from
The calibration of the bias current source in operation VDDS versus PA, with T1 = 25 °C;
mode Calibration 1 (see Table 13) is prerequisite for
adherence to the given electrical characteristics and
The necessary reference voltage VTth(T1) is then cal-
also instrumental in the determination of the chip tim-
ing (e.g. clock frequency at SCL). For setup purposes
the IBN bias current is measured using a 10 kΩ resis-
tor by pin VDDS connected to pin NC. The setpoint is
200 µA which is equivalent to a voltage drop of 2 V.
culated. The required warning temperature T2, tem-
perature coefficients TCs and TCth (see Electrical
Characteristics, Section E) and measurement value
VTs(T1) are entered into this calculation:
CFGIBN
Code k
0x0
Adr 0x01, bit 7:4
31
39−k
31
39−k
VTs(T1) + TCs · (T2 − T1)
VTth(T1) =
IBN ∼
79 %
81 %
84 %
86 %
88 %
91 %
94 %
97 %
Code k
0x8
IBN ∼
100 %
103 %
107 %
111 %
115 %
119 %
124 %
129 %
1 + TCth · (T2 − T1)
0x1
0x9
0x2
0xA
0xB
0xC
0xD
0xE
0xF
0x3
Example: For T2 = T1 + 100 K VTth(T1) must be pro-
grammed to 443 mV.
0x4
0x5
0x6
Reference voltage VTth(T1) is provided for a high
impedance measurement (10 MΩ) at output pin NA
(measurement versus VDDS) and must be set by pro-
gramming CFGTA(3:0) to the calculated value.
0x7
Table 11: Calibration of Bias Current
Temperature Sensor
The temperature monitoring is calibrated in operating
mode Calibration 3.
Example: Altering VTth(T1) from 310 mV (measured
with CFGTA(3:0)= 0x0) to 443 mV is equivalent to
143 %, the closest value for CFGTA is 0x9;
To set the required warning temperature T2 the tem-
perature sensor voltage VTs at which the warning
message is generated is first determined. To this
end a voltage ramp from VDDS towards GNDS is ap-
plied to pin PA until pin ERR displays the warning
message. The following settings are required here:
EMASKA = 0x20, EMTD = 0x00 and EPH = 0x00.
CFGTA
Code k
0x0
Adr 0x01, bit 3:0
65+3k
VTth ∼
65
65+3k
65
Code k
0x8
VTth ∼
140 %
145 %
150 %
155 %
160 %
165 %
170 %
175 %
100 %
105 %
110 %
115 %
120 %
125 %
130 %
135 %
0x1
0x9
0x2
0xA
0xB
0xC
0xD
0xE
0xF
0x3
0x4
0x5
The signal at ERR first switches from tristate to low
(on reaching the warning threshold VTs) and then from
low to tristate (on overshooting the internal hysteresis
which is not relevant to calibration). To avoid confusion
a clear change of state (from low to high) must be gen-
erated with the help of an external pull-up resistor at
pin ERR.
0x6
0x7
Notes
With CFGTA = 0xF Toff is 80 °C typ.,
with CFGTA = 0x0 Toff is 155 °C typ.
Table 12: Calibration of Temperature Monitoring
ICHAUS [ IC-HAUS GMBH ]
