L5983 查看數據表（PDF） - STMicroelectronics

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产品描述 (功能)

生产厂家

L5983

2A step-down switching regulator

STMicroelectronics 

Application informations

Table 7. Output capacitors

Manufacturer

Series

PANASONIC

ECJ

EEFCD

SANYO

TDK

TPA/B/C

C3225

L5983

Cap value (µF)

10 to 22

10 to 68

100 to 470

22 to 100

Rated voltage (V)

6.3

6.3

4 to 16

6.3

ESR (mΩ)

<5

15 to 55

40 to 80

<5

5.4

Compensation network

The compensation network has to assure stability and good dynamic performance. The loop

of the L5983 is based on the voltage mode control. The Error Amplifier is a voltage

operational amplifier with high bandwidth. So selecting the compensation network the E/A

will be considered as ideal, that is, its bandwidth is much larger than the system one.

The transfer functions of PWM modulator and the output LC filter are studied (Figure 9 on

page 19). The transfer function of the PWM modulator, from the Error Amplifier output

(COMP pin) to the OUT pin, results:

Equation 10

GPW0

=

V-----I-N--

Vs

where VS is the sawtooth amplitude. As seen in Chapter 4.1, the voltage feed forward

generates a sawtooth amplitude directly proportional to the input voltage, that is:

Equation 11

VS = K ⋅ VIN

In this way the PWM modulator gain results constant and equals to:

Equation 12

GPW0

=

V-----I-N--

Vs

=

-1--

K

=

9

The synchronization of the device with an external clock provided trough SYNCH pin can

modifies the PWM modulator gain (see Chapter 4.1 to understand how this gain changes

and how to keep it constant in spite of the external synchronization)

18/37

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