Reference Capacitor

Bypass REF with a 0.1µF capacitor. REF can source up

to 100µA.

Setting the Low-Battery Detector Voltage

To set the low-battery detector’s falling trip voltage

Ω and 500kΩ (Figures 2

and 3), and calculate R4 as follows:

R4 = R3 [

]

The rising trip voltage is higher because of the compara-

tor’s hysteresis of approximately 20mV, and can be cal-

culated by:

Connect a high-value resistor (larger than R3 + R4)

between LBI and LBO if additional hysteresis is required.

Connect a pull-up resistor (e.g., 100k

Ω) between LBO

if the low-battery detector is not used.

___________Applications Information

Layout Considerations

Proper PC board layout is essential because of high cur-

rent levels and fast switching waveforms that radiate

noise. Minimize ground noise by connecting GND, the

input bypass-capacitor ground lead, and the output filter-

capacitor ground lead to a single point (star ground con-

figuration). Also minimize lead lengths to reduce stray

capacitance, trace resistance, and radiated noise. The

traces connected to FB and LX, in particular, must be

short. Place bypass capacitor C2 as close as possible to

V+ and GND.

12V/15V or Adjustable, High-Efficiency,

______________________________________________________________________________________

11

INDUCTORS

DIODES

Sumida

CD54-180 (22µH)

Coiltronics

CTX 100-series

Matsuo

267 series

Surface Mount

Sanyo

OS-CON series

Low-ESR organic

semiconductor

Sumida

RCH855-180M

Miniature Through-Hole

PRODUCTION METHOD

Nichicon

PL series

Low-ESR electrolytics

United Chemi-Con

LXF series

Renco

RL 1284-18

Low-Cost Through-Hole

CAPACITORS

Nihon

EC10 series

Motorola

1N5817,

MUR105

Table 1. Component Suppliers

Coiltronics

(USA)

(407) 241-7876

FAX (407) 241-9339

Matsuo

(USA)

(714) 969-2491

FAX (714) 960-6492

Matsuo

(Japan)

81-6-337-6450

FAX 81-6-337-6456

Nichicon

(USA)

(708) 843-7500

FAX (708) 843-2798

Nihon

(USA)

(805) 867-2555

FAX (805) 867-2556

Renco

(USA)

(516) 586-5566

FAX (516) 586-5562

Sanyo

(USA)

(619) 661-6835

FAX (619) 661-1055

Sanyo

(Japan)

(0720) 70-1005

FAX (0720) 70-1174

Sumida

(USA)

(708) 956-0666

Sumida

(Japan)

81-3-607-5111

FAX 81-3-607-5144

United Chem-Con

(USA)

(714) 255-9500

FAX (714) 255-9400