E7765AXF datasheet(8/24 Pages) SEMTECH

8 / 24 page

2006 Semtech Corp. , Rev. 11, 7/18/06

TEST AND MEASUREMENT PRODUCTS

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E7765

Com

Computing Maximum P

puting Maximum P

puting Maximum Pooooow

wer Consum

er Consum

er Consumption

ption

The diagram below shows the power consumption of the

E7765 as a function of power supply and performance

bias settings.

Application Information

Computing the Driver Output Voltage Range

The output voltage range of the driver at the DOUT pin is

defined by two fundamental calculations. First is the rela-

tionship to the power supply voltages at the device (VCC

and VEE) and second to the range of programmability of

the DVH and DVL input voltages. Remaining in the calcu-

lated output voltage range is required to maintain all the

DC and AC accuracy specifications for the driver function.

The DOUT range relative to the power supply voltages is

straightforward and depicted in the following figure at the

output of the driver. The required DOUT range must com-

ply with the noted headrooms to the VCC and VEE power

supplies. Headrooms larger than noted is also acceptable

but must remain within the power supply recommended

operating ranges.

The DOUT range is also dependant on the allowable pro-

gramming voltages at the DVH and DVL inputs. Each of

these inputs have similar requirements for power supply

headrooms as DOUT does. These headrooms are also

depicted in the figure. Furthermore, the DVH/L inputs will

have voltage offsets and gain error specifications. These

specifications require that the DVH/L input programming

range be greater than the required DOUT voltage range if

the worst case offset and gain figures are used. The equa-

tion for the resulting minimum and maximum voltage at

DOUT is;

DOUT(MIN/MAX) = VOFFSET(MIN/MAX) + [ VIN * GAIN(MIN) ]

Solving for VIN;

IN = [ VDOUT(MIN/MAX) + VOFFSET(MIN/MAX) ] / GAIN(MIN)

To solve for the range of V

IN, first select the Vout ranges

required. For example, if we choose -2.0V for the minimum

end and +6.5V for the maximum end of V

DOUT, and an off-

set min/max of -100mV/+100mV and a minimum gain of

0.975 the equations solve as;

For -2.0V;

IN(-2V) = [ -2.0V – 100mV ] / 0.975 = -2.154V

For +6.5V;

IN(+6.5V) = [ +6.5V + 100mV ] / 0.975 = +6.769V

These resulting V

IN values then need to meet the head-

room requirements previously mentioned as well as the

absolute (relative to ground) voltage limitations specified

in the DC specifications data.

VCC

3.5V

4.0V

3.8V

3.7V

VEE

3.5V

4.0V

DVH

DVL

DOUT

Power Dissipation

Covers Complete Range of Supplies (All PON=1)

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

Min Supplies

Typ Supplies

Max Supplies

High Performance

Lower Performance

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