Functional description

L9352B

14/27

Figure 3.

Input PWM to output current range

The ON period of the input signal is measured with a 1MHz clock, synchronized with the

external 250kHz clock. For requested precision of the output current the ratio between the

frequencies of the input signal and the external 250kHz clock has to be fixed according to

the graph shown in Figure 4.

Figure 4.

Current accuracy according to the input and clock frequency ratio

The theoretical error is zero for fCLK / fIN = 125.

If the period of the input signal is longer than 132 times the period of the clock the regulator

is switched off. For a clock frequency lower than 100kHz the clock control will also disable

the regulator. For high precision applications the clock frequency and the input frequency

have to be correlated.

The output current is measured during the recirculation of the load. The current sense

resistor is in series to the free wheeling diode. If this recirculation path is interrupted the

regulator stops immediately and the status output remains low for the rest of the input cycle.

The output period is 64 times the clock period. With a clock frequency of 250kHz the output

PWM frequency is 3.9kHz. The output PWM is synchronized with the first negative edge of

the input signal. After that the output and the input are asynchronous. The first period is

250

10 16

32

90

400

800

2250

IO

(mA)

INPUT PWM(%)

±25

mA

±

10%

±6%

-8% to +6%

D03AT513A

-10%

5.6%

112.5

132

125

fCLK / fIN

0%

Regulator

switched off