FN7038 Rev 0.00

Page 16 of 16

July 17, 2001

EL1503

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frequency response (1dB peaking) for different supply

voltages and gains:

Power Control Function

The EL1503 contains two forms of power control operation.

Two digital inputs, C0 and C1, can be used to control the

supply current of the EL1503 drive amplifiers. As the supply

current is reduced, the EL1503 will start to exhibit slightly

higher levels of distortion and the frequency response will be

limited. The 4 power modes of the EL1503 are set up as

shown in the table below:

Another method for controlling the power consumption of the

EL1503 is to connect a resistor from the IADJ pin to ground.

When this pin is grounded (the normal state), the supply

current per channel is as per the specifications table on page

2. When a resistor is inserted, the supply current is scaled

according to the “IS vs RSET” graphs on page 10 in the

Performance Curves section.

Both methods of power control can be used simultaneously.

In this case, positive and negative supply currents (per amp)

are given by the equations below:

TABLE 1. OPTIMUM DRIVER FEEDBACK RESISTOR FOR

VARIOUS GAINS AND SUPPLY VOLTAGES

SUPPLY VOLTAGE

DRIVER VOLTAGE GAIN

2.5

5

10

±5V

2.7K

2.2K

2.0K

±12V

2.2K

2.0K

2.0K

TABLE 2. POWER MODES OF THE EL1503

C1

C0

OPERATION

00

IS Full Power Mode (CO or CP)

0

1

2/3 IS Power Mode (CO or CP)

1

0

1/3 IS Terminate only mode

1

1

Power down

IS+1mA C

 1 23



12.5mA

1



RSET 1k



+

-------------------------------------------





C

 0 13



12.5mA

1



RSET 1k



+

-------------------------------------------





+

+

=

IS-0 C

 1 23



12.5mA

1



RSET 1k



+

-------------------------------------------





C0



13





12.5mA

1



RSET 1k



+

-------------------------------------------





+

+

=