4.0 VREF AND VTEMP CAPACITIVE LOADING
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FIGURE 4. Loading of VREF and VTEMP
The LM56 VREF and VTEMP outputs handle capacitive loading
well. Without any special precautions, these outputs can drive
any capacitive load as shown in Figure 4 .
5.0 NOISY ENVIRONMENTS
form a 106 Hz lowpass filter. Since the thermal time constant
of the VTEMP output is much slower than the 9.4 ms time con-
stant formed by the RC, the overall response time of the
VTEMP output will not be significantly affected. For much larger
capacitors this additional time lag will increase the overall re-
sponse time of the LM56.
Over the specified temperature range the LM56 VTEMPoutput
has a maximum output impedance of 1500Ω. In an extremely
noisy environment it may be necessary to add some filtering
to minimize noise pickup. It is recommended that 0.1 μF be
added from V+ to GND to bypass the power supply voltage,
as shown in Figure 4 . In a noisy environment it may be nec-
essary to add a capacitor from the VTEMP output to ground. A
1 μF output capacitor with the 1500Ω output impedance will
6.0 APPLICATIONS CIRCUITS
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FIGURE 5. Reducing Errors Caused by Bias Current
The circuit shown in Figure 5 will reduce the effective bias
current error for VT2 as discussed in Section 3.0 to be equiv-
alent to the error term of VT1. For this circuit the effect of the
bias current on the first trip point can be defined by the fol-
lowing equations:
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