ATA6405 datasheet, PDF - EEWORLD Datasheet

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ATA6405: Description12/24V SYSTEM POWER SUPPLY IC; File Size259KB，12 Pages; ManufacturerAtmel (Microchip)

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ATA6405 Overview

12/24V SYSTEM POWER SUPPLY IC

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Features

•

Input Voltage: 8 V to 40 V

Output Voltage Linear Regulator: 5 V/50 mA/3 mA

ON_NOFF (High Active) Input

Window Watchdog

OFF Mode Quiescent current < 10 µA

Standby Mode Quiescent Current < 30 µA

Temperature Range: -40° C to 125°C

Reset Logic

Select Pin Standby/OFF Mode

Description

The ATA6405 is a fully integrated system voltage supply IC. The device is designed for

the 12/24 V board voltage system in a motor vehicle. In order to minimize power con-

sumption, a switching regulator generates a voltage for supplying the internal linear

regulator with a 5 V output voltage for microcontrollers.

To monitor the microcontroller, provision has been made for a window watchdog fea-

ture incorporating a reset logic function. The voltage system IC has three modes:

active, Standby and OFF. One control input serves to facilitate the selection between

the active and Standby modes. Another input permits the selection between the

Standby and OFF modes. In the OFF mode, a maximum quiescent current of less

than 10 µA flows through the system and in Standby mode quiescent current less than

30 µA.

12/24 V System

Power Supply IC

ATA6405

Preliminary

Rev. 4737B–AUTO–08/04

Pin Description (Continued)

Symbol

NSTB

TST_TE

TST_SCN

TCLK

SCN_IN

SCN_OUT

NTRIG

NRES

Function

Input for selecting the OFF- or Standby mode

Connections for test purposes

Not connected

Connections for test purposes

Trigger input for watchdog

Reset output

Not connected

Low - active, slope L/H

Low - active

Remarks

Connector to

⇒

OFF mode

LOW

⇒Standby

mode

Functional Description

The system voltage supply IC described here is designed for the 12/24V board voltage

supply systems in motor vehicles. To minimize power losses, provision is made for a

step-down type switching regulator to transform the battery voltage to the lowest possi-

ble initial value so as to supply the internal linear regulator with 5V. The linear regulator

is equipped with monitors controlling different voltages, currents and the temperature.

Accuracy of the regulators and monitors is provided by a bandgap acting in conjunction

with an external reference resistance on pin I_SET. In addition to the voltage regulators,

the system is further enhanced by a monitoring and control feature for microcontrollers

designed in the form of a window watchdog geared to the reset logic system. A switch-

ing input is provided for switching the system on and off. Another input controlling the

switched-off state serves to determine whether the system is to be completely switched

off (OFF mode) or whether the Standby mode is to be enabled, in which case minimum

supply of the microcontroller on pin VLR is maintained.

This product is designed for continuous operation on terminal 30 of a motor vehicle

board supply system. Accordingly, attention has been paid to ensuring minimum current

consumption in the OFF mode. The rise in supply voltage when connected to terminal

30 or when connecting up a battery must not be allowed to fall below 2V/ms. This

applies to the process of assembly and not to normal operation where minimum supply

voltage is ensured even when power fades occurs during the starting phase.

These operating modes can be set via the ON_NOFF and NSTB pins. Connecting pin

ON_NOFF to pin VB results in the ON mode being set irrespective of the NSTB pin. If

the ON_NOFF pin remains unconnected, either the OFF mode or Standby mode will be

set depending on the NSTB pin. Connection of NSTB to VB results int the OFF mode

being set. On the other hand, connecting the NSTB pin to ground potential will result in

the Standby mode being set provided that the ON mode was previously enabled. The

NSTB pin is designed for permanent wiring depending on the desired mode of

functioning.

General Features

Operating Modes:

ON/OFF/Standby

ATA6405 [Preliminary]

4737B–AUTO–08/04

ATA6405 [Preliminary]

Operating Sequence

Whenever a voltage having a typically greater value than 7.55 V is applied to the VB pin,

the switching regulator can be run up (after a brief initialization phase of approximately

100 µs) by switching from the OFF mode to the ON mode. As soon as transient build-up

is just about to transpire, the LR1 linear regulator is automatically switched on, applying

a typical output voltage of 5.6 V to the VSR pin.

As long as transient build-up has not yet taken place on the LR1 linear regulator, a reset

will be put out on the NRES pin (reset for the microcontroller supplied by the linear regu-

lator). As soon as the typical output voltage of 4.75 V has been exceeded on the VLR

pin, the reset will terminate with a delay of approximately 10 ms. This period covers the

transient build-up phase on the oscillator of the microcontroller.

In the event pin VLR falls below the typical limiting values, a reset will be put out. In the

event of excess temperature occurring or if the supply voltage falls below the specified

limiting value, both voltage regulators will be immobilized. This will also lead indirectly to

the reset state, which will remain in force until pin VB voltage drops to approximately

2.5 V.

The further sequence of operations after termination of the ON mode unleashed by

switching to ON_NOFF will depend on the wiring of the NSTB pin (also refer to the pre-

vious description). The switching regulator and linear regulator are switched off

irrespective of the NSTB pin. If the Standby mode has been selected, the first linear reg-

ulator (LR1) will be substituted by a second linear regulator of lower power capacity, this

being fed directly via the VB pin. For minimized current consumption all further functions

will switched off. These are the internal supply, the oscillator with the related voltage

monitoring controllers, the temperature controlling monitor and the watchdog. Enabling

of the Standby mode is only possible after an ON-MODE phase. Initial application of the

supply voltage will prove insufficient.

With the transfer from the Standby to the ON mode, activated by the switching pin

ON_NOFF, the pin NRES remains high in the first time (with external resistor). Due to

the functionality there is the same procedure as the one at the end of the generation of

the reset output (LOW HIGH transmission at NRES). Also see section “RESET” and

“Watchdog” on page 6.

Reset

The purpose of the reset function is to transform the microcontroller to be monitored into

a predefined state. In order to achieve this, the NRES pin is drawn internally (or exter-

nally) on ground potential. In the OFF mode the reset signal is active permanently. After

switching into the ON mode the reset signal remains for 10 ms, typically, after transient

build-up of all voltage regulators.

Outputting of the reset in the ON mode may be triggered due to a variety of different rea-

sons. In case of undervoltage at pin VLR the reset occurs immediately. The turn-off

delay is typically 10 ms and starts with the end of the event. The activation of the watch-

dog generates a reset of 10 ms. Undervoltage at pin VB or overtemperature will switch

off all voltage regulators and a reset is generated due to undervoltage at pin VLR. With

the changeover from the ON mode to the Standby mode the reset is locked in any time.

The reset is also locked with the return to the ON mode as long as all voltage regulators

have finished the transient build-up.

4737B–AUTO–08/04

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