ZXLD1100 데이터 시트보기 (PDF) - Diodes Incorporated.

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ZXLD1100

ADJUSTABLE LED DRIVER WITH INTERNAL SWITCH AND OPEN CIRCUIT PROTECTION IN SC70-6

Diodes Incorporated. 

ZXLD1100

Inductor selection

The choice of inductor will depend on available board

space as well as required performance. Small value

inductors have the advantage of smaller physical size

and may offer lower series resistance and higher

saturation current compared to larger values. A

disadvantage of lower inductor values is that they result

in higher frequency switching, which in turn causes

reduced efficiency due to switch losses. Higher inductor

values can provide better performance at lower supply

voltages. However, if the inductance is too high, the

output power will be limited by the internal oscillator,

which will prevent the coil current from reaching its

peak value. This condition will arise whenever the ramp

time (ILX(peak) x L/VIN) exceeds the nominal 5␮s

maximum ‘on’ time limit for the LX output.

The graphs opposite show the ZXLD1100 performance

for given inductor values and different manufacturers.

Recommended inductor values for the ZXLD1100 are

in the range 6.8␮H to 22␮H. The inductor should be

mounted as close to the device as possible with low

resistance connections to the LX and VIN pins.

Suitable coils for use with the ZXLD1100 are shown in

the table below:

Part No.

L

( H)

DCR

()

ISAT

(A)

Manufacturer

CMD4D11-100MC 10

0.457 0.5 Sumida

www.sumida.com

DO1608-103

10 0.16 1.1 Coilcraft

www.coilcraft.com

LQH31CN100

10 1.3 0.23 Murata

www.murata.com

LB2012Y100MR 10

0.5 0.1 Taiyo Yuden

www.t-yuden.com

Diode selection

The rectifier diode (D1) should be a fast low

capacitance schottky diode with low reverse leakage at

the working voltage. It should also have a peak current

rating above the peak coil current and a continuous

current rating higher than the maximum output load

current.

The table below gives some typical characteristics for

diodes that can be used with the ZXLD1100:

Layout considerations

PCB tracks should be kept as short as possible to

minimize ground bounce, and the ground pin of the

device should be soldered directly to the ground plane.

It is particularly important to mount the coil and the

input/output capacitors close to the device to minimize

parasitic resistance and inductance, which will

degrade efficiency. The FB pin is a high impedance

input so PCB track lengths to this should also be kept as

short as possible to reduce noise pickup. Excess

capacitance from the FB pin to ground should be

avoided.

Diode

ZHCS400

ZHCS500

VF @ 100mA (mV)

300

300

IFSM (mA)

1000

1000

Ic (mA)

400

500

IR at 30V ( A)

15

15

Package

SOD323

SOT23

SEMICONDUCTORS

10

ISSUE 4 - JULY 2004

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