LTC3543_15 Datasheet, PDF (18/20 Pages) Linear Technology – 600mA Synchronous Step Down Buck Regulator with PLL, Soft-Start and Spread Spectrum

LTC3543
TYPICAL APPLICATIONS
Spread Spectrum Application
Li-Ion
BATTERY
2.7V TO 4.2V
L
3.3μH*
V_IN
SW
10μF†
R2
LTC3543
604k
1.5V
C_FWD
10pF
V_OUT
C_OUT ^1.5V
4.7μF**
PWR_EN
RUN
V_FB
MODE CAP
GND
EXPOSED
PAD
C1
R1
2.2nF 402k
† MURATA GRM40X5R106K1H520
* TDK VLCF5020-3R3N1R6
** TDK TDKC2012X5R0J475MT
3543 TA05
Output Noise Spectrum of a Conventional Buck Switching
Converter (LTC3543 with Spread Spectrum Disabled) Showing
Fundamental and Harmonic Frequencies
–10 _{RBW = 3kHz}
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
0
6
12
18
24
30
FREQUENCY (MHz)
3543 TA06
Output Noise Spectrum of the LTC3543 Spread Spectrum Buck
Switching Converter. Note the Reduction in Fundamental and
Harmonic Peak Spectral Amplitude Compared to Conventional
Buck Switching Converter Output Noise
–10 _{RBW = 3kHz}
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
0
6
12
18
24
30
FREQUENCY (MHz)
3543 TA07
18
100
90
80
70
60
50
40
30
20
10
0
0.1
V_IN = 3.6V
1
10
100
LOAD CURRENT (mA)
1000
3543 TA08
3543fa