L9662 datasheet(56/80 Pages) STMICROELECTRONICS

56 / 80 page

Functional description

L9662

56/80

DocID028325 Rev 1

Figure 10. Transmission in asynchronous mode

High voltage mode and satellite SYNC mode

In High Voltage Mode and SYNC Mode the ICHx outputs are regulated to a higher output

voltage (VICHx_HV) than in Receive mode. In this case, the channel power supply is taken

from a separate input pin (VSYNC). Both modes are activated and deactivated by the same

SPI command. The start of the SYNC impulse is arbitrary and is created by a signal from the

μC using the INITSYNC input pin. The Sync pulse shall be initiated for all satellites based on

the rising edge of the INITSYNC input after a tSYNCDLY delay. The duration of the sync pulse

shall be based on the programmed sync pulse high time based on [D9:D8] in the MCR. If

the sync timing register has not been written the default pulse high time shall be tSYNC_high1.

The absence of an INITSYNC input rising edge does not prevent processing of incoming

messages when in HV or SYNC mode.

For Sync mode the valid sync time selections would be tSYNC_high1 and tSYNC_high2. For

High Voltage Mode the valid sync time selections would be tSYNC_high3 and tSYNC_high4. The

time selections of tSYNC_high3 and tSYNC_high4 cannot be used in normal operation because

the time duration will be longer than the receive disable time, resulting in improper

communication with the satellites. For HV mode (used only in the manufacturing or supplier

facility) if there is a short to battery flag is set then the message must be ignored.

At the start of a sync pulse there is a short period before the actual start of the sync pulse for

a channel where the current is limited to 20mA typical. This low current limit will start after

the tINITSYNCFLT time and last for 200 ns. The satellite current requirements in conjunction

with the capacitance on the pins should be verified so that the minimum satellite voltage can

be maintained.

SYNC mode

During the receiver disable time a sync pulse cannot be initiated and any change on the

INITSYNC pin will be ignored by the ASIC.The satellite SYNC mode is used to generate

automatic sync pulses for synchronous data transmission. In this mode, the output operates

in Receive Mode, but is periodically switched to a higher output voltage VICHx_HV. Thus, the

receiver decoder blocks are deactivated for the duration of the Sync pulse. To avoid

disturbance in the data flow during re-settling of the output voltage to the receive-mode

level, the receiver decoder block is deactivated for time tRECV_disable.

L9662 Datasheet(PDF) 56 Page - STMicroelectronics