13

LTC3700

3700f

series resistance (ESR). Typically, once the ESR require-

ment is satisfied, the capacitance is adequate for filtering.

The output ripple (

∆V

I

ESR

fC

OUT

RIPPLE

OUT

≈+









1

8

tor. The output ripple is highest at maximum input voltage

since

Manufacturers such as Nichicon, United Chemicon and

Sanyo should be considered for high performance through-

hole capacitors. The OS-CON semiconductor dielectric

capacitor available from Sanyo has the lowest ESR (size)

product of any aluminum electrolytic at a somewhat

met, the RMS current rating generally far exceeds the

INPUT VOLTAGE (V)

2.0

105

100

95

90

85

80

75

2.2

2.4

2.6

2.8

3700 F03

3.0

In surface mount applications, multiple capacitors may

have to be paralleled to meet the ESR or RMS current

handling requirements of the application. Aluminum elec-

trolytic and dry tantalum capacitors are both available in

surface mount configurations. In the case of tantalum, it is

critical that the capacitors are surge tested for use in

switching power supplies. An excellent choice is the AVX

TPS, AVX TPSV and KEMET T510 series of surface mount

tantalum, available in case heights ranging from 2mm to

4mm. Other capacitor types include Sanyo OS-CON,

Nichicon PL series and Panasonic SP.

Low Supply Voltage Operation

Although the LTC3700 can function down to 2.1V (typ),

the maximum allowable output current is reduced when

change as the supply is reduced down to 2.2V. Also shown

2.3V.