LTC3404IMS8 Datasheet, PDF (14/16 Pages) Linear Technology – 1.4MHz High Efficiency Monolithic Synchronous Step-Down Regulator

LTC3404
APPLICATIO S I FOR ATIO
Substituting V_OUT = 2.5V, V_IN = 4.2V, ΔI_L=120mA and 0.25Ω. In most applications, the requirements for these
f = 1.4MHz in equation (3) gives:
capacitors are fairly similar.
L
=
2.5V
1.4MHz(120mA)
⎛
⎝⎜^1−
2.5V ^⎞
4.2V ⎠⎟
=
6μH
For the feedback resistors, choose R1 = 412k. R2 can
then be calculated from equation (2) to be:
A 6.2μH inductor works well for this application. For best
efficiency choose a 1A inductor with less than 0.25Ω
R2
=
⎛
⎝⎜
V_OUT
0.8
⎞
− 1_⎠⎟ R1=
875.5k;
use
887k
series resistance.
Figure 8 shows the complete circuit along with its effi-
C_IN will require an RMS current rating of at least 0.15A at ^{ciency curve.}
temperature and C_OUT will require an ESR of less than
95
LTC3404
47pF
1
RUN
8
PLL LPF
10μF***
CER
2
7
I_TH SYNC/MODE
3
6
V_FB
4
V_{IN 5 6.2μH*}
GND
SW
22μF**
CER
V_IN
2.65V
TO 4.2V
V_OUT
2.5V
887k
3404 F08a
412k
20pF
*TOKO D63LCB A920CY-6R2M
**TAIYO-YUDEN CERAMIC JMK325BJ226MM
***TAIYO-YUDEN CERAMIC LMK325BJ106MN
V_IN = 3V
90
V_IN = 3.6V
85
80
V_IN = 4.2V
75
70
0.1
V_OUT = 2.5V
L = 6.2μH
1.0
10
100
OUTPUT CURRENT (mA)
1000
3404 F8b
Figure 8. Single Lithium-Ion to 2.5V/0.3A Regulator from Design Example
TYPICAL APPLICATIO S
Single Li-Ion to 2.5V/0.6A Regulator
Using All Ceramic Capacitors
LTC3404
1
RUN
8
PLL LPF
47pF
2
7
I_TH SYNC/MODE
3
V_FB
6
V_IN
4
GND
5
SW
4.7μH*
20pF 887k
C_OUT**
22μF
CER
V_OUT
2.5V
0.6A
*TOKO D52LC A914BYW-4R7M
**TAIYO-YUDEN CERAMIC JMK325BJ226MM
***TAIYO-YUDEN CERAMIC LMK325BJ106MN
412k
3404 TA03
V_IN
C_IN*** ^{3V TO 4.2V}
10μF
CER
3404fb
14