a8290 Allegro MicroSystems, Inc., a8290 Datasheet - Page 8

• Manufacturer Part Number: a8290
• Description: A8290 Single Lnb Supply And Control Voltage Regulator
• Manufacturer: Allegro MicroSystems, Inc.

Short Circuit Handling
If the LNB output is shorted to ground, the LNB output current
will be clamped to 900 mA, typical. If the short circuit condition
lasts for more than 48 ms, the A8290 will be disabled and the
OCP bit will be set.
Auto-Restart
After a short circuit condition occurs, the host controller should
periodically reenable the A8290 to check if the short circuit has
been removed. Consecutive startup attempts should allow at least
5 s of delay between restarts.
In-Rush Current
At start-up or during an LNB reconfiguration event, a tran-
sient surge current above the normal DC operating level can be
provided by the A8290. This current increase can be as high as
900 mA, typical, for as long as required, up to a maximum of
48 ms.
DC current
The A8290 can handle up to 700 mA per channel individually,
during continuous operation.
A8290
I
Figure 1. ODT (Overcurrent Disable Timing) Mode Timing Diagram
OUT(LNBX)
+A
0
Single LNB Supply and Control Voltage Regulator
≤t
DIS
900 mA,
typical
Start-up
2000 ms
700 mA
Continuous Operation
650 mA
Table 1. Detection Thresholds for Tone Generation Options
Tone Detection
A 22 kHz tone detector is provided in the A8290 solution. The
detector extracts the tone signal and provides it as an open-drain
signal on the TDO pin. The maximum tone out error is ±1 tone
cycle, and the maximum tone out delay with respect to the input
is 1 tone cycle. Detection thresholds are given in table 1.
Tone Generation
The A8290 solution offers four options for tone generation,
providing maximum flexibility to cover every application. The
Guaranteed
Safe Operating Area
Threshold
Threshold
Detection
Rejection
TMODE
TGATE
(Fig. 1)
(mV
(mV
Option
EXTM
Reconfiguration
PP
PP
≤t
LNB
DIS
)
)
Control
Continuous Operation
400
100
0/1
1
1
1
Control
400
100
0/1
2
1
1
Transmit
continuous
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
Control
22 kHz
signal,
logic
300
100
0/1
Circuit
Short
≤t
3
0
DIS
t
Control
22 kHz
signal
gated
logic
300
100
4
0
1
tone transmission
At least one must
be 0 to prevent
n.a.
300
100
0
Receive
n.a.
400
100
1
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