HC4GX15 Datasheet, PDF (157/668 Pages) Altera Corporation – HardCopy IV Device Handbook

Chapter 11: Power Supply and Temperature Sensing Diode in HardCopy IV Devices
11–7
External Pin Connections
A HardCopy IV device can monitor its die temperature with a TSD used with either
external or embedded analog-to-digital converter (ADC) in the device. This enables
you to control the air flow to the device. The ADC steers bias current through the
HardCopy IV TSD, measuring forward voltage and converting this reading to
temperature in the form of an 8-bit signed number (7 bits plus sign). The 8-bit output
represents the junction temperature of the HardCopy IV device and can be used for
intelligent power management.
External Pin Connections
The HardCopy IV TSD, located in the top-right corner of the die, requires two pins for
voltage reference. You can connect the TSD with an external analog-to-digital
converter (ADC) device as shown in Figure 11–4.
Figure 11–4. HardCopy IV TSD External Pin Connections
External Analog-to-Digital
Converter
TEMPDIODEP
TEMPDIODEN
TSD
HardCopy IV
The TSD is a very sensitive circuit that can be influenced by noise coupled from other
traces on the board and possibly within the device package itself, depending on
device usage. The interfacing device registers temperature based on millivolts (mV) of
difference, as seen at the TSD. Switching I/O near the TSD pins can affect the
temperature reading. Altera recommends taking temperature readings during
periods of no activity in the device.
© January 2010 Altera Corporation
HardCopy IV Device Handbook, Volume 1