EL5325A 데이터 시트보기 (PDF) - Intersil
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EL5325A Datasheet PDF : 12 Pages
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EL5325A
chip is on external clock mode. Setting B14 to low, the chip is
on internal clock mode.
CHANNEL OUTPUTS
Each of the channel outputs has a rail-to-rail buffer. This
enables all channels to have the capability to drive to within
50mV of the power rails, (see Electrical Characteristics for
details).
When driving large capacitive loads, a series resistor should
be placed in series with the output. (Usually between 5Ω and
50Ω).
Each of the channels is updated on a continuous cycle, the
time for the new data to appear at a specific output will
depend on the exact timing relationship of the incoming data
to this cycle.
The best-case scenario is when the data has just been
captured and then passed on to the output stage immediately;
this can be as short as 48µs. In the worst-case scenario this
will be 576µs when the data has just missed the cycle.
When a large change in output voltage is required, the change
will occur in 2V steps, thus the requisite number of timing cycles
will be added to the overall update time. This means that a
large change of 16V can take between 4.6ms to 5.2ms
depending on the absolute timing relative to the update cycle.
POWER DISSIPATION AND THERMAL SHUTDOWN
With the 30mA maximum continues output drive capability
for each channel, it is possible to exceed the 125°C absolute
maximum junction temperature. Therefore, it is important to
calculate the maximum junction temperature for the
application to determine if load conditions need to be
modified for the part to remain in the safe operation.
The maximum power dissipation allowed in a package is
determined according to:
PDMAX = T----J---M-----A----X--Θ-----J---A-T----A----M----A----X--
where:
• TJMAX = Maximum junction temperature
• TAMAX = Maximum ambient temperature
• θJA = Thermal resistance of the package
• PDMAX = Maximum power dissipation in the package
The maximum power dissipation actually produced by the IC
is the total quiescent supply current times the total power
supply voltage and plus the power in the IC due to the loads.
PDMAX = VS × IS + Σ[(VS - VOUTi ) × ILOADi]
when sourcing, and:
PDMAX = VS × IS + Σ(VOUTi × ILOADi)
when sinking.
Where:
• i = 1 to total 12
• VS = Supply voltage
• IS = Quiescent current
• VOUTi = Output voltage of the i channel
• ILOADi = Load current of the i channel
By setting the two PDMAX equations equal to each other, we
can solve for the RLOADs to avoid the device overheat. The
package power dissipation curves provide a convenient way
to see if the device will overheat.
The EL5325A has an internal thermal shutdown circuitry that
prevents overheating of the part. When the junction
temperature goes up to about 150°C, the part will be
disabled. When the junction temperature drops down to
about 120°C, the part will be enabled. With this feature, any
short circuit at the outputs will enable the thermal shutdown
circuitry to disable the part.
POWER SUPPLY BYPASSING AND PRINTED CIRCUIT
BOARD LAYOUT
Good printed circuit board layout is necessary for optimum
performance. A low impedance and clean analog ground plane
should be used for the EL5325A. The traces from the two
ground pins to the ground plane must be very short. The
thermal pad of the EL5325A should be connected to the analog
ground plane. Lead length should be as short as possible and
all power supply pins must be well bypassed. A 0.1µF ceramic
capacitor must be place very close to the VS, VREFH, VREFL,
and CAP pins. A 4.7µF local bypass tantalum capacitor should
be placed to the VS, VREFH, and VREFL pins.
APPLICATION USING THE EL5325A
In the first application drawing, the schematic shows the
interconnect of a pair of EL5325A chips connected to give
12 gamma corrected voltages above the VCOM voltage, and
12 gamma corrected voltages below the VCOM voltage.
External Shutdown
The EL5325A also has an external shutdown to enable and
disable the part. The SHDN pin should never be driven low.
Rather, to enable the part, the SHDN pin must be left open
(float). To disable, the SHDN pin must be driven HI (>2V).
WIth this feature, the EL5325A can be forced to shut down,
regardless of any other conditions. A simple open collector
driver is adequate to control the enable and disable function:
VSD
R1
100K
R2
100K
SHDN
Q1
PNP
EL5325A
SHDN
9
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