MIC4126 datasheet(10/22 Pages) MICROCHIP

10 / 22 page

 2019 Microchip Technology Inc.

DS20006084A-page 10

MIC4126/27/28

4.0

APPLICATION INFORMATION

Supply Bypassing

Large currents are required to charge and discharge

large capacitive loads quickly. For example, changing a

1000pF load by 16V in 25ns requires 0.8A from the

supply input.

To ensure low supply impedance over a wide frequency

range, parallel capacitors are recommended for power

supply bypassing. Low-inductance ceramic MLC

capacitors with short lead lengths (< 0.5") should be

used. A 1.0µF film capacitor in parallel with one or two

0.1µF ceramic MLC capacitors normally provides

adequate bypassing.

Grounding

When using the inverting drivers in the MIC4126 or

MIC4128, individual ground returns for the input and

output circuits or a ground plane are recommended for

optimum switching speed. The voltage drop that occurs

between the driver’s ground and the input signal

ground, during normal high-current switching, will

behave as negative feedback and degrade switching

speed.

The E-pad and ML packages have an exposed pad

under the package. It is important for good thermal

performance that this pad is connected to a ground

plane.

Control Input

Unused driver inputs must be connected to logic high

(which can be VS) or ground. For the lowest quiescent

current (< 500µA), connect unused inputs-to-ground. A

logic-high signal will cause the driver to draw up to

9mA.

The control input voltage threshold is approximately

1.5V. The control input recognizes 1.5V up to VS as a

logic high and draws less than 1µA within this range.

Power Dissipation

Power dissipation should be calculated to make sure

that the driver is not operated beyond its thermal

ratings. Quiescent power dissipation is negligible. A

practical value for total power dissipation is the sum of

the dissipation caused by the load and the transition

power dissipation (PL + PT).

Load Dissipation

Power dissipation caused by continuous load current

(when driving a resistive load) through the driver’s

output resistance is:

PL = IL2 RO

For capacitive loads, the dissipation in the driver is:

PL = f CL VS2

Transition Dissipation

In applications switching at a high frequency, transition

power dissipation can be significant. This occurs during

switching transitions when the P-channel and

N-channel output FETs are both conducting for the brief

moment when one is turning on and the other is turning

off.

PT = 2 f VS Q

Charge (Q) is read from the following graph:

Crossover Energy Loss per Transition

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