ISL59450 Datasheet, PDF (23/37 Pages) Intersil Corporation – Multiformat Video Crosspoint with Integrated Sync Separator

ISL59450
The C_SET voltage is converted to bias current for H_SYNC
and V_SYNC timing.
Internal Control Registers
The ISL59450 is initialized and controlled by a set of internal
registers that define the operating parameters of the entire
device. Communication is established between the external
controller and the ISL59450 through a standard I²C host port
interface, as described earlier. The Register Listing table on
page 24 describes all of these registers. Detailed I²C
programming information for each register is described in
“ISL59450 Serial Communications” on page 33.
Note: Do not write to reserved registers. Reserved bits in
any register should be written with 0s, unless otherwise
noted.
INITIALIZATION
It is recommended that the registers are initialized to 0x00 by
toggling the Reset pin low after powering the device. Once
the registers are initialized, set bit 0 of Miscellaneous
Register 1 to one to engage the global enable and allow the
various channels to be powered up.
Logic Control Signals
Reset is a 5V digital Input, with 3.5V logic threshold and a
300k pull-down. Tie to +5V for normal operation. Taking
Reset to 0V and back to 5V initializes all data registers to
0x00.
Power-down is a digital input with 300k pull-down. When this
pin is taken high, all analog circuitry is disabled to minimize
power consumption. In Power-down mode, the outputs are
tri-stated while the I²C interface remains active and all
register data is retained.
Crosstalk Issues
Do not set any one input to both A and B channels if the
references and modes for A and B are different. For
example, do not send CV_IN0 to both CV_OUTA and CV_OUTB
if the references for Channel A and Channel B are different
or if one channel is in slave mode while the other is in master
mode. This could cause clamping conflicts and compromise
performance.
Use the lowest bandwidth setting suitable for each
application to minimize noise, aliasing, and crosstalk. See
“Typical Application Curves” on page 19 and page 19.
23
Layout Issues
• Match channel-to-channel analog I/O trace lengths and
layout symmetry. This will minimize propagation delay
mismatches for S-video and component traces.
• All signal I/O lines should be routed over continuous
ground planes (i.e. no split planes or PCB gaps under
these lines).
• Put the proper termination resistors as close to the device
as possible.
• When testing, use high quality connectors and cables,
matching cable types and keep cable lengths to a
minimum.
• Decouple well using a minimum of 2 power supply
decoupling capacitors (1000pF, 0.01µF), placed as close
to the devices as possible. Vias between the capacitor and
the device add unwanted inductance. Larger capacitors
can be farther away.
Power Dissipation
With the high output drive capability of the ISL59450, it is
possible to exceed the +125°C absolute maximum junction
temperature under certain load current conditions.
Therefore, it is important to calculate the maximum junction
temperature for an application to determine if load conditions
or package types need to be modified to assure operation of
the amplifier in a safe operating area.
The maximum power dissipation allowed in a package is
determined according to Equation 1:
PD_MAX
=
T_{----J---M-----A----X-----–-----}T_{----A---M-----A----X--}
θ_JA
(EQ. 1)
Where:
T_JMAX = Maximum junction temperature
T_AMAX = Maximum ambient temperature
θ_JA = Thermal resistance of the package
The maximum power dissipation actually produced by an IC
is the total quiescent supply current times the total power
supply voltage, plus the power in the IC due to the load, or:
for sourcing use Equation 2:
PD_MAX
=
V_S
×
I_S
M
A
X
+
(V_S
–
V_O
UT
)
×
-^V----^O----^U----^T--
R_L
for sinking use Equation 3:
PD_MAX = V_S × I_SMAX + (V_OUT – V_S) × I_LOAD
(EQ. 2)
(EQ. 3)
Where:
V_S = Supply voltage
I_SMAX = Maximum quiescent supply current
V_OUT = Maximum output voltage of the application
R_LOAD = Load resistance tied to ground
I_LOAD = Load current
FN7510.0
February 14, 2008