ILC6370 查看數據表（PDF） - Impala Linear Corporation

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ILC6370

SOT-89 Step up Switching Regulator with Shutdown

Impala Linear Corporation 

SOT-89 Step up Switching Regulator with Shutdown

For load currents higher than 10mA, use an inductor from 47µH to

100µH. [The 100µH inductor shown in the data sheet is the most

typical used for this application.]

For load currents of around 5mA, such as pagers, use an indcutor

in the range of 100µH to 330µH. 220µH is the most typical value

used here.

The diode must be of shottkey type for fast recovery and minimal

loss. A diode rated at greater than 200mA and maximum voltage

greater than 30V is recommended for the fastest switching time

and best reliability over time. Different diodes may introduce dif-

ferent level of high frequency switching noise into the output

waveform, so trying out several sources may make the most

sense for your system.

For lighter loads, an inductor of up to 1mH can be used. The use

of a larger inductor will increase overall conversion efficiency, due

to the reduction in switching currents through the device.

For the ILC6371, using an external transistor, the use of a 47µH

inductor is recommended based on our experience with the part.

Note that these values are recommended for both 50kHz and

100kHz operation. If using the ILC6370 or ILC6371 at 180kHz,

the inductor size can be reduced to approximately half of these

stated values.

The capacitor should, in general, always be tantalum type, as tan-

talum has much better ESR and temperature stability than other

capacitor types. NEVER use electrolytics or chemical caps, as the

C-value changes below 0°C so much as to make the overall

design unstable.

Different C-values will directly impact the ripple seen on the output

at a given load current, due to the direct charge-to-voltage rela-

tionship of this element. Different C-Values will also indirectly

affect system reliability, as the lifetime of the capacitor can be

degraded by constant high current influx and outflux. Running a

capacitor near its maximum rated voltage can deteriorate lifetime

as well; this is especially true for tantalum caps which are particu-

larly sensitive to overvoltage conditions.

In general, this capacitor should always be 47µF, Tantalum,

16V rating.

For the ILC6371, much of the component selection is as described

above, with the addition of the external NPN transistor and the

base drive network. The transistor needs to be of NPN type, and

shoud be rated for currents of 2A or more. [This translates to

lower effective on resistance and, therefore, higher overall effi-

ciencies.] The base components should remain at 1kΩ and

3300kΩ; any changes need to be verified prior to implementation.

As for actual physical component layout, in general, the more

compact the layout is, the better the overall performance will be. It

is important to remember that everything in the circuit depends on

a common and solid ground reference. Ground bounce can direct-

ly affect the output regulation and presents difficult behavior to

predict. Keeping all ground traces wide will elliminate ground

bounce problems.

It is also critical that the ground pin of CL and VSS pin of the

device be the same pin on the board, as this capacitor serves two

functions: that of the output load capacitor, and that of the input

supply bypass capacitor.

Layouts for DC-DC converter designs are critical for overall

performance, but following these simple guidlines can simplify

the task by avoiding some of the more common mistakes made

in these cases. Once actual performance is completed, be

sure to double check the design on an actual manufacturing

prototype prodcut to verfy that nothing has changed which can

affect the performance.

Impala Linear Corporation

ILC6370/1 1.3

(408) 574-3939 www.impalalinear.com

July 1999 6

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