LT3045 datasheet(28/45 Pages) AD

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Data Sheet

LT83201

analog.com

Rev. A 28 of 45

The LT83201 typically operates at a switching frequency of 2MHz. Table 5 shows some examples of output capacitors

with ideal frequency characteristics when operating at switching frequencies around 2MHz. Figure 53 shows the

frequency characteristics of these capacitors. It can be seen that a combination of these capacitors minimizes the

impedance at the switching frequency on the output and keeps the impedance low enough to suppress any higher-

frequency harmonics near the switching frequency, thus achieving the lowest output ripple.

Table 5. Examples of Output Capacitors with Desirable Frequency Characteristics for 2MHz Operation

PART DESCRIPTION

MANUFACTURER/PART NUMBER

22µF, X7R, 10V, 20% 1206

MURATA, GRM31CR71A226ME15K

10µF, X7R, 25V, 10% 1206

MURATA, GRM31CR71E106KA12

4.7µF, X7S, 16V, 10% 0603

MURATA, GRM188C71C475KE21

Figure 53. Frequency Characteristics of Example Output Capacitors for 2MHz Operation

Output Voltage

The LT83201 incorporates a precision 100μA current source flowing out of the SET pin, which also connects to the

error amplifier’s non-inverting input. Figure 54 shows that connecting a resistor from SET to GND generates a

reference voltage for the error amplifier. This reference voltage is simply the product of the SET pin current and the

SET pin resistor. The error amplifier’s unity-gain configuration produces a low-impedance version of this voltage on

its inverting input, the OUTS pin, which is externally connected to the output voltage of the circuit.

Figure 54. Adjustable Reference for Error Amplifier

GRM31CR71A226ME15K (22µF)

GRM31CR71E106KA12 (10µF)

GRM188C71C475KE21 (4.7µF)

FREQUENCY (Hz)

100

10k

100k

10M

100M

0.001

0.01

0.1

100

10k

4.7µF

COUT

RSET

CSET

SET

OUTS

GND

DRIVERS

100µA

VIN

VOUT

LT83201

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