LM87

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SNAS034J – APRIL 2000 – REVISED MARCH 2013

DC Electrical Characteristics

The following specifications apply for +2.8 VDC ≤ V

+ ≤ +3.8 V

DC, Analog voltage inputs RS = 510 Ω, unless otherwise specified.

Boldface limits apply for TA = T J = TMIN to TMAX; all other limits TA = TJ = 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

≤ TA ≤ +125 °C, Vcc =

±3

°C (max)

Sensor (4) and (5)

3.3 Vdc

Temperature Error using Remote 2N3904 Sensor

−40 °C ≤ TA ≤ +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)

tC

Total Monitoring Cycle Time

(7)

0.28

sec

ADC INPUT CHARACTERISTICS

Input Resistance (All analog inputs except AIN1

130

90

k

Ω (min)

and AIN2)

AIN1 and AIN2 DC Input Current

12

μA

DAC CHARACTERISTICS

Resolution

8

Bits

0 °C

≤ TA ≤ +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

≤ TA ≤ +75 °C, V, V

+ =

±3

% (max)

3.3 V, Code = 8(8)

RL

Output Load Resistance

VO = 2.5 V

1250

Ω (min)

CL

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 TJ = TA = 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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