STPM098C datasheet(59/110 Pages) STMICROELECTRONICS

59 / 110 page

Based on single phase current measurements the sum current for each regulation loop is computed by adding the

single converted values. The current sum information is made available on PMBus™ paged register

READ_IOUTm [m = 1, 2].

Table 50. Output current sum calculation characteristics

Symbol

Parameter

Test condition

Min Typ Max Unit

Notes

Current adder output

IOUT_SUM _range1

IOUT_SUM input range on

loop 1

-480

480

IOUT_SUM _range2

IOUT_SUM input range on

loop 2

-240

240

Current adder resolution

IOUT_SUM_resolution

IOUT_SUM computation

resolution

bits Application information

IOUT_SUM_lsb

IOUT_SUM LSB

58.6

Application

information(1)

Current adder accuracy

IOUT_SUM_adc_tot_err IOUT_SUM error

mV (2)

Current adder dynamic characteristics

IOUT_SUM_latency

IOUT_SUM computation

latency

CLK_SSM_EN = 0

100

μs

Application information

1. LSB is 0.0586 A, considering DrMOS current gain is 5 mV/A (0.293 mV/5 mV/A = 0.0586 A).

2. The total error affecting the READ_IOUTm [m = 1, 2] measurement can be retrieved as the sum of the error affecting the

single MFR_READ_IOUTn [n = 1-8] conversion since the digital adder is simply introducing a sum operation on ISENn

converted codes.

READIOUTm= Σi=1NMFRREADIOUTi= Σi=1N 1ΔIOUTadclsb ISENi−VREF1CFILT 1±Gerr

±VOFS = Σi=1N 1ΔIOUTadclsb ISENi−VREF1CFILT

± Σi=1N 1ΔIOUTadclsb ISENi−VREF1CFILTGerr + NVOFS

ΔIOUTadclsb

(14)

READIOUTmERROR=± Σi=1N 1ΔIOUTadclsb ISENi−VREF1CFILTGerr + NVOFS

ΔIOUTadclsb

Where N is the number of active phases, ΔIout_adc_lsb is the phase current ADC lsb, Gerr is the gain error of the

single ISEN ADC conversion (3%), Vofs is the offset of the single ISEN ADC conversion (10 mV).

Note:

The previous relationship is always true as it refers to the single ISEN ADC voltage conversion

(MFR_READ_IOUTn [n = 1~8]) and to their sum (READ_IOUTm [m = 1, 2]). It includes only errors introduced by

STPM098C conversion on ISENn. When the LOAD current (in Amps) is to be estimated starting from the

READ_IOUTm readout additional error contributions (external to STPM098C) come into play and shall be

considered.

DrMOS current sense errors

Between the converter current information and the STPM098C converter, there is the DrMOS current sensing. To

retrieve Iload (in Amps) the multiplication by ADrMOS shall be performed.

ILOAD=ADrMOS Σi=1N 1ΔIOUTadclsb ISENi−VREF1CFILT 1±Gerr ±VOFS

=ADrMOS Σi=1N 1ΔIOUTadclsb ISENi−VREF1CFILT

± ADrMOS Σi=1N 1ΔIOUTadclsb ISENi−VREF1CFILTGerr + NVOFS

ΔIOUTadclsb

(15)

STPM098C

Functional description

DS14440 - Rev 1

page 59/110

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