LTC3883 Datasheet, PDF (57/112 Pages) Linear Technology – Single Phase Step-Down DC/DC Controller with Digital Power System Management

LTC3883/LTC3883-1
Applications Information
V_IN
6V TO 20V
5mΩ
100Ω
10nF
3Ω
10µF
1µF _100Ω
10nF
10µF
INTV_CC
TG
LTC3883
I_{IN_SNS} BOOST
V_{IN_SNS}
SW
BG
PGND
PMBus
INTERFACE
V_DD33
1.0µF
V_IN FREQ_CFG
10k
PGOOD V_{OUT_CFG}
10k
SDA V_{TRIM_CFG}
10k
SCL
ASEL
10k
ALERT
WP
10k
RUN
10k
SHARE_CLK
10k
GPIO
5k
I_SENSE+
I_SENSE–
SYNC
V_SENSE+
V_DD25
V_SENSE–
V_DD33
TSNS
I_TH
GND
1.0µF
D4
0.1µF
1µF
M1
22µF
50V
1.0µH
M2 2.2k
0.2µF
2200pF MMBT3906
6.04k
10nF
V_OUT
3.3V
+
15A
C_OUT
530µF
6V
3883 F28
C_OUT: 330μH SANYO 4TPF330ML, 2× 100µF AVX 12106D107KAT2A
L: COILCRAFT XPL7070 1µH
M1: RENESAS RJK0305DPB
M2: RENESAS RJK0330DPB
Figure 28. High Efficiency 500kHz 3.3V Step-Down Converter
All other user defined parameters must be programmed
into the NVM. The GUI can be utilized to quickly set up
the part with the desired operating parameters.
The inductance values are based on a 35% maximum ripple
current assumption (5.25A). The highest value of ripple
current occurs at the maximum input voltage:
L
=
f
•
V_OUT
∆I_{L(MAX )}

1–

V_OUT
V_{IN(MAX )}



The controller will require 1.05µH. The nearest standard
value is 1µH. At the nominal input the ripple will be:
∆I_L(NOM)
=
V_OUT
f •L

1–

V_OUT
V_IN(NOM)



The ripple will be 4.79A (32%). The peak inductor current
will be the maximum DC value plus one-half the ripple
current or 17.39A. The minimum on time occurs at the
maximum V_IN, and should not be less than 90ns:
( ) ^tON(MIN)
=
V_OUT
V_{IN(MAX )}
•
f
=
20V
1.8V
500kHz
= 180ns
The Vishay IHLP4040DZ-11 1µH (2.3mΩ DCR_TYP at 25°C)
is the chosen inductor.
Assuming the temperature measurement of the inductor
temperature is accurate and C1 is set to 0.2µF, R_D is infinite
and removed from the equations.
R1=
(DCR
at
L
25°C)
•
C1
=
1µH
2.5mΩ • 0.2µF
= 1.37k
3883f
57