L9300 datasheet(51/178 Pages) STMICROELECTRONICS

51 / 178 page

Switching Period Programming

HW current control feedback can work both at variable or fixed frequency, the operating mode can be selected

through a dedicated configuration bit in the CTRLCFG register; in case variable frequency is chosen the digital

control loop may vary the PWM period during transients in order to improve the settling time; in such a

configuration the programmed PWM period becomes a target for the inner period control loop. In HW mode the

PWM switching period of each solenoid driver can be programmed through a dedicated 11bit SPI register

(CTRLCFG), the period can be programmed to:

•

(N*64+1)*Tref_PWM where Tref_PWM = 125 ns in fixed frequency mode and N is the programmed value

in the register

•

(N*64+2)*Tref_PWM where Tref_PWM = 125 ns in variable frequency mode and N is the programmed

value in the register; the switching period control loop reaches stable point of operation when the effective

frequency is between the SPI register target value and (N*64+2 + (1/Kfi – 1))*Tref_PWM with an average

value over time equal to (N*64+2+(1/Kfi – 1)/2)*Tref_PWM) so it is affected by PI period control loop

settings.

In both HW modes (fixed and variable frequency) the minimum operating period is clamped by setting N = 12 for

N ≤ 12 values.

Table 30. Fixed and variable period programming

PWM_CTRLCFG

Period when in Fixed Frequency

Period when in variable Frequency

769*125n [s]

770*125n [s]

769*125n [s]

770*125n [s]

769*125n [s]

770*125n [s]

…

769*125n [s]

770*125n [s]

833*125n [s]

834*125n [s]

…

2046

130945*125n [s]

130946*125n [s]

2047

131009*125n [s]

131010*125n [s]

The resulting PWM period of solenoid drivers is internally checked and feedback in the PWMSENSE SPI register:

the period is checked against reference Tmin and Tmax values, outside these limits a flag TMOUT is set in the

SPI register PWMSENSE to inform that the control loop is working at unusual value.

The Tmin is fixed at 800*Tref_PWM while the Tmax value is set at 133334*Tref_PWM. Tmax limit only applies for

variable frequency mode. Both in variable and fixed frequency mode, in case no PWM signal is generated after

Tmax value, the period meter is reset at 196609*Tref_PWM and the average current is calculated.

Dither Programming

On the target current a dither modulation can be superimposed (this functionality can be disabled).

Dither modulation can be configured through SPI registers setting the number of steps to be implemented, their

amplitude and their duration Tstep: once the previous parameters are defined the achieved dither waveform is

similar to the one shown in the next figure.

Dither step duration can be computed using the formula:

Tstep= (1+ (M+1)*2N)*tref_dth

where tref_dth=128*125ns;

the mantissa value (M) can be programmed through 5 bit , from 0 to 31, of dedicated register DITHPGM, while the

exponent value (N) value can vary from 0 to 7 (3 bit programming) in the same register.

Amplitude of the single step can be calculated multiplying the value set by Dither current step amplitude bits in the

DITHPGM SPI register times the dither resolution Dth_res (equal to 1LSB of current set-point resolution); total

dither step number in a period is four times the value written in the Dither current step bits of DITHPGM register.

Total amplitude of the dither waveform is clamped between -1024 and 1023 LSB.

L9300

Valve drivers

DS12258 - Rev 5

page 51/178

L9300 датащи(PDF) 51 Page - STMicroelectronics

L9300 датащи(HTML) 51 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL