ZXCL250 View Datasheet(PDF) - Zetex => Diodes
Part Name
Description
Manufacturer
ZXCL250 Datasheet PDF : 11 Pages
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ZXCL Series
APPLICATIONS INFORMATION
Enable Control
A TTL compatible input is provided to allow the
regulator to be shut down. A low voltage on the Enable
pin puts the device into shutdown mode. In this mode
the regulator circuit is switched off and the quiescent
R
current reduces to virtually zero (typically less than
10nA) for input voltages above the minimum operating
threshold of the device. A high voltage on the Enable
pin ensures normal operation.
C
The Enable pin can be connected to VIN or driven from
an independent source of up to 10V maximum. (e.g.
CMOS logic) for normal operation. There is no clamp
diode from the Enable pin to VIN, so the VIN pin may be
at any voltage within its operating range irrespective of
the voltage on the Enable pin. However input voltage
rise time should be kept below 5ms to ensure
consistent start-up response.
Figure 1 Circuit Connection
Current Limit
The ZXCL devices include a current limit circuit which
restricts the maximum output current flow to typically
230mA. Practically the range of over-current should be
considered as minimum 160mA to maximum 800mA.
The device’s robust design means that an output short
circuit to any voltage between ground and VOUT can be
tolerated for an indefinite period.
Thermal Overload
Td
Figure 2 Start up delay (Td)
Thermal overload protection is included on chip. When
the device junction temperature exceeds a minimum
125°C the device will shut down. The sense circuit will
re-activate the output as the device cools. It will then
cycle until the overload is removed. The thermal
overload protection will be activated when high load
currents or high input to output voltage differentials
cause excess dissipation in the device.
Start up delay
A small amount of hysteresis is provided on the Enable
pin to ensure clean switching. This feature can be used
to introduce a start up delay if required. Addition of a
simple RC network on the Enable pin provides this
function. The following diagram illustrates this circuit
connection. The equation provided enables calculation
of the delay period.
Td(NOM)
=
RCIn
VIN
VIN − 1.5
Calculation of start up delay as above
ISSUE 7 - AUGUST 2002
8
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