DVRFD615X2 Development Board

The SMB connectors are used to supply input signals. Test

points are straight forward, Vcc supply voltage, IN1 and IN2 input

signals, GND ground for entire board. It is suggested to operate

the board at 12 V for general testing.

R1, R3 limits input signal current but is not mandatory for all driv-

er applications; it is more for general protection of the driver. R2,

R4 termination resistors matches the typical 50 Ω output imped-

ance of most bench top signal generators. The input of the gate

driver can operate without R1, R3 and R2, R4, where R2 and R4

can be removed, if desired, in the case that the input signal gen-

erator can’t support the loading. In most cases the output level of

the signal generator will have to be increased in order to com-

pensate for the input termination load.

Bulk storage capacitors C7, C8, C9, C10 provide energy storage

local to the driver. During switching of the output stage of the

driver, parasitic inductance of any wire and trace between the

power supply and driver can inhibit fast delivery of energy to the

driver. This will result in a voltage drop along the inductance and

will cause the voltage at the Vcc pins to sag. To counter this,

large valued bulk storage capacitors are placed as close to the

Vcc pins of the driver to supply energy right at the driver pins.

Tantalum capacitors are used and suggested for use as they can

release their stored energy very quickly into the Vcc pins. Alumi-

num electrolytic capacitors are not used or recommended for

bulk storage capacitors due to their high values of ESR, or Equiv-

alent Series Resistance, that slows energy delivery.

.

Figure 5– Sag in supply voltage at Vcc pins due to high

series resistance from bulk storage capacitors

The network of bypass capacitors are made up of C1-C6,

C11-C16 and includes a wide spread of values, 0.001 μF,

0.01 μF, and 0.1 μF. The purpose of the capacitance

spread is to produce over-lapping response curves that

lower the insertion impedance over a wider band. The by-

pass capacitors can be viewed as low pass filters, but the

generally ignored series inductance causes a notch or V-

shaped response in the impedance curve as frequency

goes up. Figures 12-16 represent the progression of a sin-

gle ideal capacitor response to the parallel combination of

multiple capacitor networks.

Figure 6– Ideal capacitor frequency response

Figure 7– Capacitor frequency response due to

self inductance

Figure 8– Over-lapping impedance curves

Figure 9– Broadband impedance lowered