Philips Semiconductors Product data sheet
NE1619HECETA4 Temperature and voltage monitor
2004 Oct 05
13
Temperature data is represented by a digital 8-bit byte or word in
two’s complement format with a resolution of 1 °C. Theoretically, the
temperature value can be from –128 °C to +127 °C but, practically,
the operation range is limited to (0 °C, 120 °C). Here are some of
temperature values and data:
Table 8.
TEMPERATURE VALUE (°C) TEMPERATURE DATA
+127 0111 1111
+126 0111 1110
+100 0110 0100
+25 0001 1001
+1 0000 0001
0 0000 0000
–1 1111 1111
–25 1110 0111
–50 1100 1110
Voltage measurement
The NE1619 provides 5 analog inputs for directly monitoring the
power supplies typically found in a PC or multiservice equipment,
having nominal values of +2.5 V, +3.3 V, +5.0 V, +12.0 V and V
CCP
(2.25 V). The device also monitors its own V
DD
whose nominal
value is 3.3 V. Note: at power-up, the device Pin 11 is defaulted to its
12V
IN
function. These inputs are internally attenuated by on-chip
resistor networks to the reference levels that are then multiplexed to
a 8-bit Delta-Sigma A-to-D converter for converting into digital data.
Each V
IN
input is overall scaled in such a way that the decimal value
of the data for its nominal voltage value is equal to 192. It means
that the overall step size of the conversion for each V
IN
is equal to
1
/
192
of its nominal value. Reading data are stored in the V
IN
reading
registers and are also compared with the limits stored in the V
IN
limit
registers in order to set the voltage flag bits in the status registers as
described in Tables 3 and 4.
The V
IN
data, different from the temperature data, is represented by
a digital 8-bit byte or word in straight format with a resolution LSB
equal to
1
/
192
of the nominal value, and has any value from 0 to 255.
This is how to calculate the V
IN
error from the V
IN
reading at any
input including V
DD
:
Resolution in volts: LSB = (V
IN
nominal in volt)/192
Full scale in volts: FS= 255 * LSB
Reading value in volts: V
IN
value =
(decimal value of V
IN
reading) * LSB
Reading error in volts: V
IN
error = (V
IN
value) – (V
IN
applied)
VIN error in % of FS: V
IN
error % = 100*(V
IN
error)/FS
Applied value < 0 results in a reading of about 0
Applied value > FS results in a reading of about 255
Input safety
Since the power supply voltages will appear directly at V
IN
pins, a
small external resistor, about 500 Ω, should be connected in series
with each pin in order to prevent damaging the power supplies due
to accidental short. These resistors are recommended but not
necessary. No external resistor-divider should be used for the V
IN
pins because of the effect of the internal input resistors, about
140 kΩ at each pin, on the divider accuracy.
Processor Voltage ID (VID)
The NE1619 provides 5 digital pins (VID0–VID4) to read the
processor voltage ID code and store it into the VID registers so that
the code can be read over the SMBus:
VID register: bit 0–bit3 reflect VID0–VID3 respectively
VID4 register: bit 0 reflects VID4
Because the VID4 function of 12V
IN
/VID4 pin (Pin 11) is not selected
at power-up (default function of this pin is 12V
IN
), the process of
selecting this pin must be performed, if VID4 is needed, by setting
(to 1) bit 5 (12V
IN
/VID4 SELECT) of the configuration register.
The default value of bit 0 of the VID4 register is 0.
The VID inputs should not be left floating because they are not
internally biased. If they are not used then they should be connected
to either GND or V
DD
with resistors.
Limit data
High and Low limits for temperatures and voltages should be
programmed into the limit registers using the format as described
above. During monitoring cycle, the measured data is automatically
compared with the limits and flag bits in the status registers are set
accordingly to the results. The assignment of the status bits are
listed in Tables 3 and 4.
Status registers
Results of limits comparisons are reflected by status or flag bits
stored in the status register 1 and 2. If the reading is within the limits
then the corresponding flag bit will be cleared to 0. Otherwise, it will
be set to 1. Status data can be read over the SMBus. Notice that
because the flag bits are automatically updated at every monitoring
cycle, their states only reflect the last measurements.
Diode fault status
The hardware connection at the diode pins (D+ and D–) are also
checked at the measurement of external temperature and the fault
condition is indicated by the flag bit 6 of the status register 2. This bit
is set to 1 if either short or open circuit fault is detected.
RESET output function
The NE1619 Pin 16 can be selected as a reset pulse output. When
this function is selected and the reset pulse is initiated, this pin will
output a single (minimum 20 ms) low state pulse.
The reset output function is selected by setting (to 1) the RESET
ENABLE bit (bit 7) of the VID register. Thereafter, the reset pulse is
generated whenever the RESET bit (bit 4) of the configuration
register is programmed to change from 0 to 1.
Because Pin 16 becomes an open-drain output when it is selected
as an output, an external pull-up resistor, about 100 kΩ is needed
for the output operation. This will restrict the address function on
Pin 16 to being high at power-up. Therefore, if multiple NE1619’s
are connected on the same bus, only one can have this function
enabled at one time.
