9

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 5

Ω and

50

Ω).

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:

where:

•

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.

when sourcing, and:

when sinking.

Where:

• i = 1 to total 12

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

and CAP pins. A 4.7µF local bypass tantalum capacitor should

APPLICATION USING THE EL5325A

In the first application drawing, the schematic shows the

interconnect of a pair of EL5325A chips connected to give

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:

---------------------------------------------

=

(

×

[]

+

×

=

×

()

+

×

=

SHDN

100K

100K

PNP

SHDN

EL5325A

EL5325A