Rev. 4737BAUTO08/04
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 A
Standby Mode Quiescent Current < 30 A
Temperature Range: -40
C to 125C
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 A flows through the system and in Standby mode quiescent current less than
30 A.
12/24 V System
Power Supply IC
ATA6405
Preliminary
2
ATA6405 [Preliminary]
4737BAUTO08/04
Block Diagram/Application Circuit
Application Notes
1.
It is strongly recommended to connect the blocking capacitors at VB1, VB2,
VSR, VLR as closely as possible to the pins PGND, AGND.
2.
It is strongly recommended to use capacitors with very low ESR.
3.
The 47 nF capacitors are of ceramic types.
4.
It is strongly recommended to connect the resistor R
1
as closely as possible to
the pins I_SET and AGND.
Bandgap,
Current/Bias
Oscillator
Window
watchdog
VVB
Monitor
R
1
20k
D
1
VSR
CVSR
L
1
Temperature
Monitor
Buck
Converter
NTRIG
NRES
I_SET
Reset-
Logic
SR0
6.5 V/50 mA
5 V (
2%)/50 mA
400 kHz
165C
Period 11.2 ms
Window 6.40 ms
300 H
7.55 V
VLR
5 V
CVLR
47 F
AGND
NSTB
LX3
Standby: 5 V/3 mA
2
22 F + 47 nF
2
33 F
+ 47 nF
+ 47 nF
TCLK
SCN_IN
TST_SCN
TST_TE
PGND
(5 V)
SCN_OUT
VB2
LX2
VB1
LX1
DGND
PGND
K30
(9.0 to 40.0 V)
ON
Mode Select
Standby
VLR
ON_NOFF
OFF
ON
CVB
Micr
o
-
c
ont
rol
l
e
r
Regulator
LR1
LR2
Regulator
Control
+
+
+
3
ATA6405 [Preliminary]
4737BAUTO08/04
Pin Configuration
Figure 1. Pinning QFN28 7x7 (pitch 0.8 mm)
MLP 7x7mm
0.8mm pitch
28 lead
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
ATA6405
NC
TST_SCN
TST_TE
NSTB
ON_NOFF
VB2
VB1
NC
NRE
S
NT
R
I
G
S
CN_O
U
T
S
CN_I
N
TC
L
K
NC
NC
NC
LX
3
LX
2
LX
1
NC
NC
DGND
I_SET
AGND
VLR
VSR
PGND
PGND
Pin Description
Pin
Symbol
Function
Remarks
1
DGND
Grounding connection for digital stages
2
I_SET
Connection for reference resistance
3
AGND
Grounding connection for analog stages
4
VLR
Output from LR1
Output from LR2
5 V/50 mA (ON_mode)
5 V/3 mA (Standby mode)
5
VSR
Feedback input of switching regulator and input of
linear regulator LR1
6
PGND
Grounding connection for power stages
7
PGND
Grounding connection for power stages
8
NC
Not connected
9
NC
Not connected
10
LX3
Switching output of switching regulator
11
LX2
Switching output of switching regulator
12
LX1
Switching output of switching regulator
13
NC
Not connected
14
NC
Not connected
15
VB1
Voltage supply
16
VB2
Voltage supply
17
ON_NOFF
Input for selecting between ON and OFF or
Standby mode
Connector to
VB
ON mode
LOW
OFF mode
4
ATA6405 [Preliminary]
4737BAUTO08/04
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.
General Features
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.
Operating Modes:
ON/OFF/Standby
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.
18
NSTB
Input for selecting the OFF- or Standby mode
Connector to
VB
OFF mode
LOW
Standby mode
19
TST_TE
Connections for test purposes
20
TST_SCN
Connections for test purposes
21
NC
Not connected
22
NC
Not connected
23
TCLK
Connections for test purposes
24
SCN_IN
Connections for test purposes
25
SCN_OUT
Connections for test purposes
26
NTRIG
Trigger input for watchdog
Low - active, slope L/H
27
NRES
Reset output
Low - active
28
NC
Not connected
Pin Description (Continued)
Pin
Symbol
Function
Remarks
5
ATA6405 [Preliminary]
4737BAUTO08/04
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 s) 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.
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