TK65428MTL/428 查看數據表（PDF） - Toko America Inc

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TK65428MTL/428

STEP-DOWN CONVERTER WITH BATTERY MONITOR

Toko America Inc  

TK654xx

ADVANCED INFORMATION

NOISE CONSIDERATIONS (CONT.)

COIL

The coil magnetic field can also be a source of noise. This noise is more characteristic of radiated Electromagnetic

Interference (EMI). This radiated noise can interfere with RF communications systems if care is not taken by the system

designer. A shielded coil can improve this source of EMI.

SNUBBER

When the inductor current flowing through the output diode decays to zero, the parasitic capacitance at the switch pin

(pin 3) resulting from the internal switch and external diode has energy which rings back into the inductor. This high

frequency ringing is an undesirable source of radiated noise. Fortunately, due to the low amount of energy in this ringing,

a simple RC snubber as shown in Figure 5 easily eliminates it. In low noise applications the RC snubber is recommended,

although an efficiency penalty of approzimately 2% will result.

VOUT = 3 V

C1

22 µF

L1

100 µH

D1

LL 103

LBO

VOUT

SW

220

PF

1K

LBI

GND

VIN

VIN = 5 V

FIGURE 5: OPTIONAL SNUBBER

Page 16

September 1999 TOKO, Inc.

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