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LM4140

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SNVS053F – JUNE 2000 – REVISED SEPTEMBER 2016

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8.1.5 Multilayer Ceramic Capacitors

Surface-mountable multilayer ceramic capacitors may be an attractive choice because of their relatively small

physical size and excellent RF characteristics.

However, they sometimes have an ESR values lower than the minimum required by the LM4140, and relatively

large capacitance change with temperature. The manufacturer's datasheet for the capacitor must be consulted

before selecting a value. Test results of LM4140 stability using multilayer ceramic capacitors show that a

minimum of 0.2 µF is usually required.

Table 4 shows the multilayer ceramic capacitors that have been verified as suitable for use with the LM4140.

Table 4. Surface-Mount Ceramic Capacitors Selection

Guide

CAPACITOR (µF)

MANUFACTURER

PART NUMBER

2.2

Tokin

1E225ZY5U-C203

2.2

Murata

GRM42-6Y5V225Z16

4.7

Tokin

1E475ZY5U-C304

8.1.6 Reverse Current Path

The P-channel Pass transistor used in the LM4140 has an inherent diode connected between the VIN and VREF

pins (see Figure 25).

Figure 25. Internal P-Channel Pass Transistor

Forcing the output to voltages higher than the input, or pulling VIN below voltage stored on the output capacitor

by more than a Vbe, forward biases this diode and current flows from the VREF terminal to VIN. No damage to the

LM4140 occurs under these conditions as long as the current flowing into the output pin does not exceed 50 mA.

8.1.7 Output Accuracy

Like all references, either series or shunt, the after assembly accuracy is made up of primarily three components:

initial accuracy itself, thermal hysteresis, and effects of the PCB assembly stress.

LM4140 provides an excellent output initial accuracy of 0.1% and temperature coefficient of 6ppm/°C (B Grade).

For best accuracy and precision, the LM4140 junction temperature must not exceed 70°C.

The thermal hysteresis curve on this datasheet are performance characteristics of three typical parts selected at

random from a sample of 40 parts.

Parts are mounted in a socket to minimize the effect of PCB's mechnical expansion and contraction. Readings

are taken at 25°C following multiple temperature cycles to 0°C and 70°C. The labels on the X axis of Figure 26

indicate the device temperature cycle prior to measurement at 25°C.