STPM098C datasheet(79/110 Pages) STMICROELECTRONICS

79 / 110 page

Figure 65. Digital compensator simplified block diagram

Digital Compensator

PID

LP2

LP1

ADC_Ln

VADC_IN_Ln

PWM

Mod

The PID LP filter 1 and filter 2 can be programmed through a dedicated PMBus™ register as follows:

MFRFILTERPREPOST14:7= TckTck+τLP128

(35)

MFRFILTERPREPOST6:0= TckTck+τLP227

(36)

The PID Kn parameters for the n-th loop can be programmed through a dedicated PMBus™ register as follows:

MFRPID118:0=8Kp+KdTck

(37)

MFRPID215:0=216KiTCK

(38)

MFRPID315:0=KdTck

(39)

Where:

Tck is the system clock period.

MFR_FILT_PRE_POST [6:0] are the dedicated PMBus™ configuration bits.

In order to prevent compensator persistent integration after a heavy to light load transition, a digital error clamp

limit can be set through a dedicated PMBus™ command as follows:

VERRCLAMP=ΔLSB× 63−VERRCLAMP5:0

(40)

Where:

ΔLSB is the minimum slew rate step [2 mV].

VERR_CLAMP [5:0] is the dedicated PMBus™ configuration bits [0 ~ 126 mV].

The default value is VERR_CLAMP = 0x00.

To enhance control loop dynamic performances during load transients, STPM098C implements a function that

doubles the controller proportional gain factor when digital error exceeds a programmable threshold.

Transient gain boost function can be configured by means of TGB_CONFIG register as follows:

TGBTH=TGBTHlsb×TGBCONFIG7:2

(41)

Where:

TGB_TH_lsb is the minimum drooping step [2 mV].

TGB_CONFIG [7:2] are the dedicated PMBus™ configuration bits [0 mV ~ 126 mV].

The default value is TGB_CONFIG [7:2] = 0x3F.

TGBEN=TGBCONFIG7:2

(42)

Where:

TGB_CONFIG [1:0] are the dedicated PMBus™ configuration bits:

00, TGB disabled.

01, TGB is enabled only when N ≥ 2 (N is the number of active phases).

10, TGB always enabled.

10, TGB always enabled. TBG threshold = 2x TGB_TH

For further details concerning loop compensator and deeper details on mathematical aspects, refer to the

Application note: “STPM098C_AN_PID_setting”.

STPM098C

Functional description

DS14440 - Rev 1

page 79/110

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