se97b NXP Semiconductors, se97b Datasheet - Page 7

• Manufacturer Part Number: se97b
• Description: Ddr Memory Module Temp Sensor With Integrated Spd
• Manufacturer: NXP Semiconductors

NXP Semiconductors
SE97B_1
Product data sheet
7.3.1 EVENT pin output voltage levels and resistor sizing
7.3 EVENT output condition
The EVENT output indicates conditions such as the temperature crossing a predefined
boundary. The EVENT modes are very configurable and selected using the configuration
register (CONFIG). The interrupt mode or comparator mode is selected using CONFIG[0],
using either TCRIT/UPPER/LOWER or TCRIT only temperature bands (CONFIG[2]) as
modified by hysteresis (CONFIG[10:9]). The UPPER/LOWER (CONFIG[6]) and TCRIT
(CONFIG[7]) bands can be locked.
temperature versus time, with the corresponding behavior of the EVENT output in each of
these modes.
Upon device power-up, the default condition for the EVENT output is high-impedance to
prevent spurious or unwanted alarms, but can be later enabled (CONFIG[3]). CONFIG[3]
does not have to be cleared (e.g., set back to (0)) before changing CONFIG[2] or
CONFIG[0]. EVENT output polarity can be set to active HIGH or active LOW
(CONFIG[1]). EVENT status can be read (CONFIG[4]) and cleared (CONFIG[5]).
If the EVENT output is enabled (CONFIG[3] = 1) and the part is switched between
Interrupt mode and Comparator mode or vice versa, the EVENT output may glitch during
the change.
If the device enters Shutdown mode (CONFIG[8]) with asserted EVENT output, the output
either de-asserts (default) or remains asserted (frozen) depending on SMBUS[4].
The EVENT open-drain output is typically pulled up to a voltage level from 0.9 V to 3.6 V
with an external pull-up resistor, but there is no real lower limit on the pull-up voltage for
the EVENT pin since it is simply an open-drain NMOS pull-down output. It could be pulled
up to 0.1 V and would not affect the output. From the system perspective, there will be a
practical limit. That limit will be the voltage necessary for the device monitoring the
interrupt pin to detect a HIGH on its input. A possible practical limit for a CMOS input
would be 0.4 V. Another thing to consider is the value of the pull-up resistor. When a low
supply voltage is applied to the drain (through the pull-up resistor) it is important to use a
higher value pull-up resistor, to allow a larger maximum signal swing on the EVENT pin.
Rev. 01 — 27 January 2010
DDR memory module temp sensor with integrated SPD
Figure 4
shows an example of the measured
© NXP B.V. 2010. All rights reserved.
SE97B
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