Cypress CY8CKIT-025, Руководство пользователя

Страница: 29 / 86

CY8CKIT-025 PSoC® Precision Analog Temperature Sensor Expansion Board Kit Guide, Doc. # 001-65791 Rev. *J 29
Hardware
Figure 4-4. Diode Circuit Diagram and Diode Connected Transistor
In Figure 4-4 (a), D1 and D2 are diode connected transistors (See Figure 4-4 (b)). While measuring
the temperature using diode D1, MUX1 channel1 and MUX2 channel2 are active. While measuring
the temperature using diode D2, MUX1 channel2 and MUX2 channel1 are active.
By passing two currents I
1
and I
2
and measuring the respective voltages V
1
and V
2
, the temperature
is calculated using equation 8. The ADC measures a negative voltage in one of the two cases, which
can be negated in firmware to make it positive. Measurements are made in four-wire configuration to
avoid series resistance error.
M
U
X
1
IDAC
M
U
X
2
IDAC
ADC
D1
D2
(a) Diode Circuit Diagram (b) Diode Connected Transistor