DS75365 datasheet(5/8 Pages) NSC

5 / 8 page

TLF7560 – 7

FIGURE 2 Interconnection of DS75365 Devices

with 1103-Type Silicon-Gate MOS RAM

Typical Applications

The fast switching speeds of this device may produce unde-

sirable output transient overshoot because of load or wiring

inductance A small series damping resistor may be used to

reduce or eliminate this output transient overshoot The op-

timum value of the damping resistor depends on the specific

load characteristics and switching speed A typical value

would be between 10X and 30X (

Figure 3 )

Note RD j 10X to 30X (Optional)

TLF7560 – 8

FIGURE 3 Use of Damping Resistor to Reduce or

Eliminate Output Transient Overshoot in Certain

DS75365 Applications

Thermal Information

POWER DISSIPATION PRECAUTIONS

Significant power may be dissipated in the DS75365 driver

when charging and discharging high-capacitance loads over

a wide voltage range at high frequencies The total dissipa-

tion curve shows the power dissipated in a typical DS75365

as a function of load capacitance and frequency Average

power dissipation by this driver can be broken into three

components

PT(AV) e PDC(AV) a PC(AV) a PS(AV)

where PDC(AV) is the steady-state power dissipation with the

output high or low PC(AV) is the power level during charging

or discharging of the load capacitance and PS(AV) is the

power dissipation during switching between the low and

high levels None of these include energy transferred to the

load and all are averaged over a full cycle

The power components per driver channel are

PDC(AV) e

PLtL a PHtH

PC(AV) j CVC2f

PS(AV) e

PLHtLH a PHLtHL

where the times are as defined in

Figure 4

PL PH PLH and PHL are the respective instantaneous lev-

els of power dissipation and C is load capacitance

The DS75365 is so designed that PS is a negligible portion

of PT in most applications Except at very high frequencies

tL a tH n tLH a tHL so that PS can be neglected The total

dissipation curve for no load demonstrates this point The

power dissipation contributions from all four channels are

then added together to obtain total device power

The following example illustrates this power calculation

technique Assume all four channels are operating identical-

ly with C e 100 pF f e 2 MHz VCC1 e 5V VCC2 e 20V

VCC3 e 24V and duty cycle e 60% outputs high

(tH T e 06) Also assume VOH e 20V VOL e 01V PS is

negligible and that the current from VCC2 is negligible when

the output is low

On a per-channel basis using data sheet values

PDC(AV) e (5V)

4mA4J a(20V) b22mA

J a(24V)

22mA

J( (06)a (5V) 31mA

J a

(20V)

0mA4J a(24V) 16mA

J( (04)

PDC(AV) e 58 mW per channel

PC(AV) j (100 pF) (199V)2 (2 MHz)

PC(AV) j 79 mW per channel

For the total device dissipation of the four channels

PT(AV) j 4 (58 a79)

PT(AV) j 548 mW typical for total package

TLF7560 – 9

FIGURE 4 Output Voltage Waveform

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