L9908 datasheet(86/153 Pages) STMICROELECTRONICS

86 / 153 page

DCMn_READ = 101100011110101 (binary) → - 9995 (decimal)

CS_INRANGE_CFG = 011 (CM input ADC range +/-90 mV)

ILOAD RSHUNT = - 9995 *6.293 μV = -62.898 mV

Latency associated to digital format current information update (SPI) in auto-triggering mode can be retrieved in

the following table.

Table 76. Current monitors A/D auto-triggering latency

Symbol

Parameter

Min

Typ

Max

Unit

Notes

CM_in_latency

CM Input latency

Tclk

Application information(1)

1. CSMn_SYNC_COUNT_CFG1 (16/24/32/40 Tclk) + SAR (10 Tclk) + DSP (5 to 11 Tclk).

5.13.3

D/A conversion

After DSP operations digital conversion is forwarded to an analog output channel which provides the processed

current information to the analog domain.

Figure 63. D/A conversion simplified block diagram

In order to better fit dynamic range and maximize the output S/N with respect to the externally connected

microcontroller A/D, two successive digital operations are performed.

First is the truncation from signed 15 bits to signed 11 bits.

The current measurement coded in a signed 15-bit word is firstly converted to a signed 11-bit word by taking the

11MSB.

Second is Shift and Rescale (sign removal and offset adding).

From the resulting processed word the 11MSB without sign are taken and a fixed selectable offset OFS is added

(shift).

The shift amount for the specific channel can be configured by means of dedicated SPI bits in order to adjust the

current monitor output range to the μC ADC input range as follows:

Table 77. Current monitors output offset configuration bits

CSMn_OFS1

CSMn_OFS0

Description

0LSB DAC

90LSB DAC

1024LSB DAC

1024LSB DAC (Default)

L9908

Current monitors

DS13546 - Rev 3

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