LTC7151S datasheet(28/44 Pages) AD

28 / 44 page

Data Sheet

LT83203/LT83205

analog.com

Rev. B

28 of 44

The LT83203/LT83205 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 51

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 51. Frequency Characteristics of Example Output Capacitors for 2MHz Operation

Output Voltage

The LT83203/LT83205 incorporates a precision 100μA current source flowing out of the SET pin, which also connects

to the error amplifier’s non-inverting input. Figure 52 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 52. 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

LT83203/

LT83205

LTC7151S Datasheet(PDF) 28 Page - Analog Devices

LTC7151S Datasheet(HTML) 28 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

Datasheet Download

Link URL