ZXLD1322 Ver la hoja de datos (PDF) - Diodes Incorporated.
Número de pieza
componentes Descripción
Fabricante
ZXLD1322
Diodes Incorporated.
ZXLD1322 Datasheet PDF : 17 Pages
| |||
A Product Line of
Diodes Incorporated
ZXLD1322
Application Notes
Setting Peak Coil Current
The peak current in the coil is set by the resistor (RSENSE) between the switch emitter and ground according to:
ISWPEAK
=
50mV
RSENSE
The minimum peak current will depend on operating mode, coil inductance and supply voltage range. The maximum peak
current must not exceed the specified value for the switch. (See Application circuits for details)
Setting LED Current
The nominal average LED current is given by:
ILED (NOM) =
100mV
RM
Where RM is the external resistor connected between pins M_VIN and VIN.
This current can be adjusted to a lower value by applying a dc control voltage or PWM control signal to the ADJ pin.
DC Control
The LED current can be adjusted over a 10% to 100% range by connecting a variable resistor RADJ from the ADJ pin to
ground to vary the DC voltage at the ADJ pin. RADJ forms the lower part of a resistive divider and the internal 100kΩ resistor
between the ADJ and VREF pins forms the upper part. A value of 1MΩ for RADJ will therefore give a maximum current of
91% of ILED (nom) and the device will be turned off when the voltage on the ADJ pin falls below 28mV, corresponding to an
RADJ value of approximately 5kΩ. If required, an end-stop resistor in series with RADJ can be used to maintain the voltage on
the ADJ pin above the turn-on threshold.
Using a logarithmic potentiometer for RADJ will give an approximately linear variation of output current with shaft rotation.
(Fig 1)
If required, the maximum output current can be restored to 100% by adjusting the value of the LED current monitor resistor
(RM). The tolerance of the internal 100k resistor and RADJ should be taken into account when calculating output current.
The ADJ pin is clamped internally to a voltage of 575mV (nom), to limit maximum average output current to approximately
115% of ILED(nom).
ZXLD1322
Document number: DS32166 Rev. 3 - 2
Fig. 1
10 of 17
www.diodes.com
April 2010
© Diodes Incorporated
Share Link: