Taking into account this temperature coefficient and the initial tolerance of the resistors, the output impedance

of the device does not exceed 4kΩ. In an extremely noisy environment adding filtering can be necessary to

minimize noise pickup. TI recommends adding a CBy-pass = 0.1µF capacitor between +VS and GND to bypass

the power supply noise voltage, as shown in Figure 8-3. Adding a capacitor (CLoad) from VO to ground can be

necessary. A 1µF output capacitor with the 4kΩ output impedance forms a 40Hz low-pass filter. Because the

thermal time constant of the LM50 and LM50HV is much slower than the 25ms time constant formed by the RC,

the overall response time of the device is not significantly affected. For much larger capacitors, this additional

time lag increases the overall response time of the LM50 and LM50HV.

TI device

OUT

Heavy Capacitive Load, Wiring, and more.

To A High-

Impedance Load

Figure 8-2. LM50 and LM50HV No Decoupling Required for Capacitive Load

TI device

VO

Heavy Capacitive Load, Wiring, Etc.

CLoad = 1µF

CBy-pass = 0.1µF

Figure 8-3. LM50 and LM50HV With Filter for Noisy Environment

To avoid glitch of start-up power supply (input) response especially when CBy-pass is not used (as shown in

Figure 6-20, Figure 8-4 and Figure 8-5) on LM50 (new chip) and LM50HV devices, a minimum CLoad must

be placed between VO and ground especially when LM50 (new chip) and LM50HV devices are utilized in the

comparator circuits.

Time (

s)

-20

20

60

100

140

180

220

-1

-1

0

0

1

1

2

2

3

3

4

4

5

5

6

6

VO →

VO →

VO →

 +VS

+VS = 3.3V

VO (at -40C)

VO (at 25C)

VO (at 150C)

Figure 8-4. Start-up response to +VS = 3.3V Step

(When tr = 1μs, No CLoad and CBy-pass)

Time (

s)

-20

20

60

100

140

180

220

-10

-1

0

0

10

1

20

2

30

3

40

4

50

5

60

6

VO →

VO →

VO →

 +VS

+VS = 36V

VO (at -40C)

VO (at 25C)

VO (at 150C)

Figure 8-5. Start-up Response to +VS = 36V Step

(When tr = 1μs, No CLoad and CBy-pass)

The minimum CLoad capacitor is varied over different operating temperature range and power supply ramp rate

as shown in the Table 8-2. Please noted that the rise time (tr) can be translated to ramp rate of power supply

(SR) by: SR (V/μs) = 0.8 × +VS (V) / tr (μs).

www.ti.com

LM50, LM50HV

SNIS118I – JULY 1999 – REVISED OCTOBER 2025

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