Datasheet

LM87
www.ti.com
SNAS034J APRIL 2000REVISED MARCH 2013
DC Electrical Characteristics
The following specifications apply for +2.8 V
DC
V
+
+3.8 V
DC
, Analog voltage inputs R
S
= 510 Ω, unless otherwise specified.
Boldface limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other limits T
A
= T
J
= 25 °C.
(1)
Typical Limits Units
Symbol Parameter Conditions
(2) (3)
(Limits)
POWER SUPPLY CHARACTERISTICS
Normal Mode, Interface 0.7 2.0 mA (max)
Inactive
I
+
Supply Current
Shutdown Mode 0.5 mA
TEMPERATURE-TO-DIGITAL CONVERTER CHARACTERISTICS
Temperature Error using Internal Diode ±3 °C
Temperature Error using Remote Pentium Diode 0 °C T
A
+125 °C, Vcc = ±3 °C (max)
Sensor
(4)
and
(5)
3.3 Vdc
Temperature Error using Remote 2N3904 Sensor 40 °C T
A
+125 °C, Vcc ±4 °C (max)
(4)
and
(5)
= 3.3 Vdc
Resolution 8 bits 1.0 °C (min)
LM87 ANALOG-TO-DIGITAL CONVERTER CHARACTERISTICS
Resolution 8 bits
TUE Total Unadjusted Error
(6)
±2 % (max)
DNL Differential Non-Linearity ±1 LSB (max)
t
C
Total Monitoring Cycle Time
(7)
0.28 sec
ADC INPUT CHARACTERISTICS
Input Resistance (All analog inputs except AIN1
130 90 kΩ (min)
and AIN2)
AIN1 and AIN2 DC Input Current 12 μA
DAC CHARACTERISTICS
Resolution 8 Bits
0 °C T
A
+75 °C, V
+
= 3.3 -3.3 % (min)
V, Code = 255
V
+
= 3.3 V, 3/4 Scale, code +3.7 %
DAC Error
192
0 °C T
A
+75 °C, V, V
+
= ±3 % (max)
3.3 V, Code = 8
(8)
R
L
Output Load Resistance V
O
= 2.5 V 1250 Ω (min)
C
L
Output Load Capacitance 20 pF (max)
(1) Parasitics and or ESD protection circuitry are shown in Figure 2 for the LM87's pins. The nominal breakdown voltage of the zener D3 is
6.5 V. Care should be taken not to forward bias the parasitic diode, D1, present on pins: A0/NTEST_OUT, A1 and DACOut/NTEST_IN.
Doing so by more than 50 mV may corrupt a temperature or voltage measurement.
(2) Typicals are at T
J
= T
A
= 25 °C and represent most likely parametric norm.
(3) Limits are specified to TI's AOQL (Average Outgoing Quality Level).
(4) The Temperature Error specification does not include an additional error of ±1°C, caused by the quantization error.
(5) The Temperature Error will vary less than ±1°C over the operating Vcc range of 2.8V to 3.8V.
(6) TUE (Total Unadjusted Error) includes Offset, Gain and Linearity errors of the ADC.
(7) Total Monitoring Cycle Time includes all diode checks, temperature conversions and analog input voltage conversions. Fan tachometer
readings are determined separately and do not affect the completion of the monitoring cycle.
(8) This is the lowest DAC code specified to give a non-zero DAC output.
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