LT1304-5.0V UTC, LT1304-5.0V Datasheet - Page 9

• Manufacturer Part Number: LT1304-5.0V
• Description: MICROPOWER DC/DC CONVERTERS
• Manufacturer: UTC

UTC LT1304/LT1304-3.3V/LT1304-5.0V
LAYOUT/INPUT BYPASSING
The LT1304 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 LT1304 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.
UTC
UNISONIC TECHNOLOGIES CO., LTD.
500mA/DIV
Figure 5. Start-Up Response with 1μF/1MΩComponents
in Figure 2 Added. Input Current Is More Controlled. V
Reaches 5V in6ms.Output Drives 20mA Load.
10V/DIV
2V/DIV
1000
V
V
900
800
700
600
500
400
LINEAR INTEGRATED CIRCUIT
OUT
SHDN
I
IN
10
Figure 6.Peak Switch Current vs R
1ms/DIV
RLIM(kΩ
100
LIM
1304 F05
Value
1000
OUT
QW-R103-018,A
9