ZXLD1321DCATC Diodes Zetex, ZXLD1321DCATC Datasheet - Page 11

• Manufacturer Part Number: ZXLD1321DCATC
• Description: IC LED DRVR WHITE BCKLGT 14-TDFN
• Manufacturer: Diodes Zetex
• Type: Backlight, White LEDr

Specifications of ZXLD1321DCATC

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Flash/Torch
• Type - Secondary: High Brightness LED (HBLED), White LED
• Frequency: 600kHz
• Voltage - Supply: 2 V ~ 12 V
• Mounting Type: Surface Mount
• Package / Case: 14-TDFN
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 1A
• Internal Switch(s): Yes
• Efficiency: 85%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Other names: ZXLD1321DCATR

Application notes
Setting peak coil current
The peak current in the coil is set by the resistor (R
according to
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
Where R
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 R
from the ADJ pin to ground to vary the dc voltage at the ADJ pin. R
resistive divider and the internal 100k resistor between the ADJ and VREF pins forms the upper
part. A value of 1M
the device will be turned off when the voltage on the ADJ pin falls below 28mV, corresponding to
an R
used to maintain the voltage on the ADJ pin above the turn-on threshold.
Using a logarithmic potentiometer for R
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 (R
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 I
Issue 1 - January 2008
© Zetex Semiconductors plc 2008
I
I
LED
SWpeak
ADJ
(
nom
M
value of approximately 5k . If required, an end-stop resistor in series with R
is the external resistor connected between pins M_VIN and M_LOAD.
)
Rsense
50
mV
100
R
for RADJ will therefore give a maximum current of 91% of I
mV
M
M
). The tolerance of the internal 100k resistor and R
LED
(nom).
ADJ
will give an approximately linear variation of output
11
SENSE
) between the switch emitter and ground
ADJ
forms the lower part of a
ZXLD1321
www.zetex.com
LED
ADJ
ADJ
(nom) and
should be
can be
ADJ