MAX17841B datasheet(5/33 Pages) MAXIM

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(VDCIN=5V,VAA = VDDL=3.3V,TA = TMIN to TMAX, unless otherwise noted, where TMIN=-40°CandTMAX=+105°C.Typicalvalues

are at TA=+25°C.Operationiswiththerecommendedapplicationcircuit.)

Note 2: Differentialsignal(VRXP-VRXN)whereVRXP,VRXNdonotexceedacommon-modevoltagerangeof±25V.

Note 3: All parameters measured based on differential signal.

Note 4: Guaranteedbydesignandnotproductiontested.

Note 5: Fall time measured 90% to 10%, rise time measured 10% to 90%.

Note 6: Measuredfromfallingedgeof8thSCLKcycleoftheWR_NXT_LD_QSPIcommandbyte(B0h).

Note 7: tPROP is the maximum propagation delay through a slave device in a given direction. Refer to the UART slave device data

sheet for the actual delay. The number of UART slave devices is denoted by n.

Note 8: Measured from end of 12th bit of stop character.

Note 9: Parameter tREGWRis the minimum amount of time needed to write a register in the nth slave device of the daisy-chain. It is

measuredfromthestartoftheSPItransactionWR_NXT_LD_Q(B0h)thatinitiatestransmissionofaWRITEALLmessage

towhenthenthdevicereceivesavalidWRITEALLmessage.Forexample,for4MHzSPIfrequency,2MbpsUARTbaud

rate, n = 10 and tPROP=3xtBIT, tREGWR=2μs+65μs+15μs=82μs.

Note 10:Computation of tREGWR consists of three terms: 1) duration of the SPI transaction, 2) partial duration of the UART

message,and3)propagationdelayoftheUARTmessage.ThefirsttermequalsthenumberofbitsintheSPItransaction

(8) x the SPI bit time (1 / fSCLK).ThesecondtermequalsthetimefromthestartoftheWRITEALLmessagetothefirst

STOPbitofthelastPECnibble.ThelastPECnibbleisthe11thcharacterinthemessage.Witheachcharacterlasting12

UARTbittimes,thereare11x12=132bittimesfromthestartofthemessagetotheendofthelastPECnibble.Sincethe

writeoccursjustbeforethetwoSTOPbitsofthe11thcharacter,thetermisactually130xtBIT. The third term is the propa-

gationdelayrequiredfortheWRITEALLmessagetogettothenthdevice.

Figure 1. SPI Timing Diagram (Example of Reading Register 0x1B with Data 80h and Transaction Terminated Prematurely)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

TxValidtoRxValidUpStack

Delay(Note7)

tRXUP

n x

tPROP

TxValidtoRxValidDownStack

Delay(Note7)

tRXDN

n x

tPROP

EndofSTOPCharacterto

RX_Stop_INTFlagTrue

(Note8)

tINT

2 x tBIT

SPI START to UART Slave

DeviceRegisterWriteDelay

(Notes9,10)

tREGWR

8 / fSCLK+

130xtBIT+

n x tPROP

Electrical Characteristics (continued)

tCSSO

tCH

tDS

tDH

tDO

tCL

tCSWH

SCLK

DIN

DOUT

Maxim Integrated │ 5

MAX17841B

Automotive SPI Communication Interface (ASCI)

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