IC-PI datasheet(21/49 Pages) ICHAUS

21 / 49 page

preliminary

iC-PI PROGRAMMABLE 12-BIT

Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

Rev B1, Page 21/48

BIAS CURRENT SOURCE AND TEMPERATURE SENSOR

Bias Current Calibration

The calibration of the bias current source in operation

mode Calibration 1 (refer to Table 18 for an overview

of operating modes) is required to adhere to the given

Electrical Characteristics and also instrumental in the

determination of the chip timing (e.g. clock frequency

at SCL).

The IBN bias current is measured by connecting pin

VDDS and pin NB with a 10 kΩ resistor. When the volt-

age drop is 2 V, the bias current is adjusted to its target

value of 200 µA.

CFGIBN

Addr. 0x00, bit 3:0

Code k

IBN ∼ 31

39−k

Code k

IBN ∼ 31

39−k

0x0

79 %

0x8

100 %

0x1

81 %

0x9

103 %

0x2

84 %

0xA

107 %

0x3

86 %

0xB

111 %

0x4

88 %

0xC

115 %

0x5

91 %

0xD

119 %

0x6

94 %

0xE

124 %

0x7

97 %

0xF

129 %

Table 16: Bias Current

Temperature Sensor Calibration

The temperature monitoring is calibrated in operating

mode Calibration 3 (refer to Table 18 for an overview of

operating modes).

First, the temperature sensor voltage at which the warn-

ing message is generated, VTs, must be determined.

A voltage ramp from VDDS towards GNDS is applied

to pin PA until pin ERR pulls low textcolormarkupA2(at

approx. 4.4 V when coming from 5.0 V).

The following settings are required for this measure-

ment: EMASKA = 0x20 (excessive temperature warn-

ing enabled), EMTD = 0x00 (shortest alarm indication

time), and EPH = 0x00 (alarm output active low).

Note that the signal at pin ERR switches from tristate to

low (on reaching VTs) and already at just 25 mV lower

from low to tristate (on overshooting the temperature

shutdown threshold, which is not relevant to calibration).

To avoid confusion, a clear change of state (from high

→

low → high) should be generated using an external

pull-up resistor at pin ERR.

Example: VTs(T1) is approx. 640 mV, measured from

VDDS versus PA, with T1 = 25 °C;

The necessary warning activation threshold, VTth(T1),

is then calculated. The required warning temperature

T2, temperature coefficients TCs and TCth (see Electri-

cal Characteristics, Section E), and measurement value

VTs(T1) are entered into this calculation:

VTth(T1) =

VTs(T1) + TCs · (T2 − T1)

1 + TCth · (T2 − T1)

Example: for T2 = T1 + 100 K VTth(T1) must be pro-

grammed to 434 mV.

Reference voltage VTth(T1) is provided for a high

impedance measurement (10 MΩ) at output pin NA

(measurement against VDDS) and must be set to the

calculated value by programming CFGTA(3:0).

Example: altering VTth(T1) from 315 mV (measured

with CFGTA(3:0)= 0x0) to 434 mV is equivalent to

138 %, the closest value for CFGTA is 0x8;

CFGTA

Addr. 0x01, bit 3:0

Code k

VTth ∼ 65 + 3.25k

Code k

VTth ∼ 65 + 3.25k

0x0

100 %

0x8

140 %

0x1

105 %

0x9

145 %

0x2

110 %

0xA

150 %

0x3

115 %

0xB

155 %

0x4

120 %

0xC

160 %

0x5

125 %

0xD

165 %

0x6

130 %

0xE

170 %

0x7

135 %

0xF

175 %

Notes

CFGTA = 0xC: Tw is approx. 85 °C, and Toff is

approx. 97 °C typically.

CFGTA = 0x8: Tw is approx. 125 °C, and Toff is

approx. 137 °C typically.

Table 17: Temperature Monitoring

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