AN487 APPLICATION NOTE

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Figure 2. Cross section of the BDC mixed technology.

In the 70’s class B circuits and DC circuits allowed output power in the range of 70W. By 1980 ,with the

introduction of switching techniques in power ICs, output powers up to 200W were reached; with BCD

technology the output power increased up to 400W.

FUNCTIONS AND BLOCK DIAGRAM

The complete block diagram of the high power L4970A is shown in fig.3. Each block is analysed in the

following.

Figure 3. Block diagram of the 10A monolithic regulator L4970A.

POWER SUPPLY

The device is provided with an internal stabilized power supply ( Vstart =12V ), that provides the supply

voltage to the analog and digital control blocks and also the supply voltage to the bootstrap section. The

Vstart voltage supplies also the internal Reference Voltage section that provides accurate 5.1V voltage to

the control loop. Through trimming techniques the 5.1V reference is within +- 2% limits.