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L4969MD

SYSTEM VOLTAGE REGULATOR WITH FAULT TOLERANT LOW SPEED CAN-TRANSCEIVER

STMicroelectronics 

L4969

1 FUNCTIONAL DESCRIPTION

1.1 General Features

The L4969 is a monolithic integrated circuit which provides all main functions for an automotive body

CAN network.

It features two independent regulated voltage supplies V1 and V2, an interrupt and reset logic with internal clock

generator, Serial Interface and a low speed CAN-bus transceiver which is supplied by a separate third voltage

regulator (V3).

The device guarantees a clearly defined behavior in case of failure, to avoid permanent CAN bus errors.

The device operates in four basic modes, with additional programming for V1 Standbymodes in CTCR:

Mode

Sleep #1

V1 V2 V3 Timer/WDC

CAN-IF

Ityp

LP1, LP0

(CTCR)

Off Off Off

Off

Standby 40u

x,x

Remarks

No Timer based wakeup

Sleep #2 Off Off Off On (250KHz) Standby 80u

x,x

Timer active

Standby #1(*1) On Off Off

Off

Standby 170u 1,1

No Watchdog or Timer

Standby #2(*1) On Off Off On (250KHz) Standby 210u 1,0

Watchdog or timer active

Standby #3 On Off Off On (1MHz) Standby 440u 0,0

Watchdog or timer activ, POR default

RXOnly Off Off On On (1MHz) RX-Only 4mA x,x Active during Busactivity to filter ID, auto-

matic fall back to Sleep when Bus idle

Normal On On On On (1MHz) Normal 5mA x,x

No Currents from CAN or Regulators

(*1) Note, that in order to enter either Standby #1 or Standby #2 the Startup-Watchdog has to be acknowledged (see Chapter 1.2), in Standby

#1, the Window Watchdog has to be disabled as described in Chapter 2.5, to allow the decativation of the internal oscillator.

1.1.1 V1 Output Voltage

The V1 regulator uses a DMOS transistor as an output stage. With this structure very low dropout voltage is

obtained. The dropout operation of the standby regulator is maintained down to 4V input supply voltage. The

output voltage is regulated up to the transient input supply voltage of 40V. With this feature no functional inter-

ruption due to overvoltage pulses is generated. The output 1 regulator is switched off in sleep mode.

1.1.2 V2 Output Voltage

The V2 regulator uses the same output structure as the output 1 regulator except to being short circuit proof to

VS, and to be rated for the output current of 200mA. The V2 output can be switched on and off through a ded-

icated enable bit in the control register. In addition a tracking option can be enabled to allow V2 follow V1 with

constant offset. This feature allows consistent A/D conversion inside the µC (supplied by V1) when the convert-

ed signals are referenced to V2. The maximum voltage that can be applied to V2 is VS + 0.3V up to a max VS

of 40V.

1.1.3 V3 Output Voltage

The third voltage regulator of the device generates the supply voltage for the internal logic and the CAN-trans-

ceiver. In operating mode it is capable of supplying up to 200mA in order to guarantee the required short circuit

current for the CAN_H driver. The sleep and operating modes are switched through a dedicated enable bit.

1.1.4 Internal Supply Voltage

A low power sleep mode regulator supplies the internal logic in sleep mode.

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