UTCUT2306/UT2306-3.3V/UT2306-5.0V

LINEAR INTEGRATED CIRCUIT

9

QW-R103-029,A

2V/DIV

Figure 5. Start-Up Response with 1μF/1MΩComponents

Reaches 5V in6ms.Output Drives 20mA Load.

1ms/DIV

500mA/DIV

10V/DIV

1304 F05

1000

RLIM(kΩ

100

10

1000

900

800

700

600

500

400

LAYOUT/INPUT BYPASSING

The UT2306 high speed switching mandates careful attention to PC board layout. Suggested component place-ment

is shown in Figure 7.The input supply must have low impedance at AC and the input capacitor should be placed as

indicated in the figure. The value of this capacitor depends on how close the input supply is to the IC. In situations

where the input supply is more than a few inches away from the IC, a 47µF to 100µF solid tantalum bypass capacitor

is required. If the input supply is close to the IC, a 1µF ceramic capacitor can be used instead. The UT2306 switches

current in 1A pulses, so a low impedance supply must be available. If the power source (for example, a 2AA cell

battery) is within 1 or 2 inches of the IC, the battery itself provides bulk capacitance and the 1µF ceramic capacitor

acts to smooth voltage spikes at switch turn-on and turn –off. If the power source is far away from the IC, inductance

in the power source leads results in high impedance at high frequency. A local high capacitance bypass is then

required to restore low impedance at the IC.