L4969UR-E datasheet(16/46 Pages) STMICROELECTRONICS

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Functional description

L4969UR-E, L4969URD-E

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Doc ID 022587 Rev 2

Functional description

3.1

General features

The L4969UR 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 Standby

modes in CTCR:

3.1.1

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 4 V input supply voltage. The output voltage is regulated up to the transient input

supply voltage of 40 V. With this feature no functional interruption due to overvoltage pulses

is generated. The output 1 regulator is switched off in sleep mode.

3.1.2

V2 output voltage

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

short circuit proof to VS. The V2 output can be switched on and off through a dedicated

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

microcontroller (supplied by V1) when the converted signals are referenced to V2. The

maximum voltage that can be applied to V2 is VS + 0.3 V up to a max VS of 40 V.

Table 15.

Operating mode description

Mode

Timer/WDC

CAN-IF

Ityp

LP1, LP0

(CTCR)

Remarks

Sleep #1

Off Off Off

Off

Standby

40µ

x,x

No Timer based wakeup

Sleep #2

Off Off Off On (250Khz) Standby

80µ

x,x

Timer active based on tOSCslow

Standby #1(1)

On Off Off

Off

Standby 170µ

1,1

No Watchdog or Timer

Standby #2(1)

On Off Off On (250KHz) Standby 210µ

1,0

Watchdog or timer active based on

tOSCslow

Standby #3

On Off Off

On (1MHz)

Standby 440µ

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

Note, that in order to enter either Standby #1 or Standby #2 the Startup-Watchdog has to be acknowledged, in Standby #1, the Window

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

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