Datasheet
MaxPossible_I=
V
R
SHUNT_MAX
SHUNT
MaxPossible_I=0.064
Minimum_LSB=
Max_Expected_I
32767
Minimum_LSB=1.831 10´
-6
Maximum_LSB =
Max_Expected_I
4095
Maximum_LSB = 14.652 10´
-6
Cal=trunc
0.04096
Current_LSB R´
SHUNT
Cal=4311
Power_LSB=20Current_LSB
Power_LSB=38 10´
-6
TMP512
TMP513
www.ti.com
SBOS491A –JUNE 2010– REVISED MAY 2011
Calibration Example 2 (Overflow Possible)
This design example uses the nine-step procedure for calibrating the TMP512/13 where overflow is possible.
Figure 33 illustrates how the same procedure is performed using the automated TMP512/13EVN software. The
same numbers used in the nine-step example are used in the software example shown in Figure 33. Note also
that Figure 33 illustrates which results correspond to which step (for example, the information entered in Step 1
is circled in Figure 33 and labeled).
1. Establish the following parameters:
V
BUS_MAX
= 32
V
SHUNT_MAX
= 0.32
R
SHUNT
= 5
2. Determine the maximum possible current using Equation 15:
(15)
3. Choose the desired maximum current value: Max_Expected_I, ≤ MaxPossible_I. This value is selected
based on system expectations.
Max_Expected_I = 0.06
4. Calculate the possible range of current LSBs. This calculation is done by first computing a range of LSB's
that is appropriate for the design. Next, select an LSB withing this range. Note that the results will have the
most resolution when the minimum LSB is selected. Typically, an LSB is selected to be the nearest round
number to the minimum LSB.
(16)
(17)
Choose an LSB in the range: Minimum_LSB < Selected_LSB < Maximum_LSB
Current_LSB = 1.9 × 10
–6
Note:
This value was selected to be a round number near the Minimum_LSB. This section allows for good
resolution with a rounded LSB.
5. Compute the calibration register using Equation 18:
(18)
6. Calculate the Power LSB using Equation 19. Equation 19 shows a general formula; because the bus voltage
measurement LSB is always 4mV, the power formula reduces to calculate the result.
(19)
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