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4.4
L4998 Safety Power Regulator ASIC
The L4998 integrated circuit is intended for automotive applications.The main feature set is
described below:
●
Boost regulator able of sourcing up to 90mA output current
●
Buck regulator operating in Continuous Conduction Mode able of sourcing up to 250 mA
output current
●
One 5.0V linear regulator (V
CC
) able of sourcing up to 200mA output current
●
Regulator soft-start control (C
SLEW
)
●
Buck voltage out-of-regulation detection (BCKFLT)
●
V
CC
out-of-regulation detection with reset delay (RST)
●
Current-limit and thermal shutdown protection
●
Package: PowerSSO14
4.5 Satellite/Sensor
interface
The devices provide output current limited a 60 mA to drive up to six satellites or four satellites
and two Hall sensors.
The L9658/L9654 will monitor the current flow from its output pin and “demodulate” the current
to be decoded using Manchester protocol. Decoded satellite message is communicated to an
external microprocessor via SPI.
4.5.1 Features
●
Interface with 6 satellite sensors
●
Programmable independent current trip points for each satellite channel
●
Support Manchester protocol for satellite sensors
●
Supports for variable bit rate detection
●
Independent current limit and fault timer shutdown protection for each satellite output
●
Short to ground and short to battery detection and reporting for each satellite channel
●
5.5MHz SPI interface
●
Satellite message error detection
●
Hall effect sensor support on satellite channels 3 and 4.
4.5.2 Functional
description
Each output channel senses the current drawn by the remote satellite sensor; the circuit
modulates the load current into logic voltage levels for post processing by a manchester
decoder.
The L9658/L9654 decode satellite messages based on Manchester decoding, each of the six
satellite channels have a Manchester decoder that can be enabled or disabled through a
register.
Each output has a short circuit protection by independent current limit. When a short circuit
occurs the output becomes current limited, a fault timer latch the output off and a fault condition
bit is reported via SPI.That output returns to normal operation when it is re-enabled via SPI and
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