LTC3850EUF#PBF Linear Technology, LTC3850EUF#PBF Datasheet - Page 28

• Manufacturer Part Number: LTC3850EUF#PBF
• Description: IC CNTRLR STP DWN SYNC 28-QFN
• Manufacturer: Linear Technology
• Series: PolyPhase®r
• Type: Step-Down (Buck)r

Specifications of LTC3850EUF#PBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.8 ~ 23.3 V
• Current - Output: 100mA
• Frequency - Switching: 250kHz ~ 780kHz
• Voltage - Input: 4 ~ 24 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-QFN
• Primary Input Voltage: 24V
• No. Of Outputs: 2
• Output Current: 100mA
• No. Of Pins: 28
• Operating Temperature Range: -40°C To +85°C
• Msl: MSL 1 - Unlimited
• Supply Voltage Range: 4V To 24V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

LTC3850/LTC3850-1
APPLICATIONS INFORMATION
voltage will decrease as V
switching frequency. If a separate 5V supply is connected to
EXTV
The inductance values are based on a 35% maximum
ripple current assumption (1.75A for each channel). The
highest value of ripple current occurs at the maximum
input voltage:
Channel 1 will require 3.2µH, and Channel 2 will require
1.9µH. The next highest standard values are 3.3µH
and 2.2µH. At the nominal input voltage (12V), the ripple
will be:
Channel 1 will have 1.45A (29%) ripple, and Channel 2 will
have 1.4A (28%) ripple. The peak inductor current will be
28
V
L =
OUT1
3.3V
∆I
5A
CC
L(NOM)
, INTV
f • ∆I
L1, L2: COILTRONICS HCP0703
M1, M2: VISHAY SILICONIX Si4816BDY
C
OUT1
V
3.3µH
C
100µF
X2
OUT1
OUT
L1
=
6.19k
, C
L(MAX)
63.4k
CC
1%
33pF
1%
OUT2
V
f • L
OUT
will remain at 5V even if V
: TAIYO YUDEN JMK325BJ107MM
20k
1%



M1



1−
1−
1.33k
1%
IN
V
V
IN(NOM)
IN(MAX)
Figure 14. High Efficiency Dual 500kHz 3.3V/1.8V Step-Down Converter
V
4.7µF
V
approaches 5V, lowering the
4.75k
1%
OUT
OUT
1800pF
0.1µF






0.1µF
100pF
2.2Ω
D3
0.1µF
IN
TG1
BOOST1
SW1
BG1
MODE/PLLIN
I
SENSE1
SENSE1
RUN1
V
I
decreases.
V
LIM
TH1
TK/SS1
IN
FB1
PGOOD
+
–
LTC3850
1µF
SGND
EXTV
FREQ/PLLFLTR
CC
SENSE2
SENSE2
BOOST2
TK/SS2
INTV
PGND
RUN2
the maximum DC value plus one-half the ripple current,
or 5.725A for Channel 1 and 5.7A for Channel 2.
The minimum on-time occurs on Channel 1 at the maximum
V
With I
can be calculated by using the minimum value for the
maximum current sense threshold (40mV).
The equivalent R
SW2
V
TG2
BG2
I
TH2
FB2
IN
CC
+
–
0.1µF
R
t
, and should not be less than 90ns:
5A +
ON(MIN)
SENSE(EQUIV)
40mV
LIM
D4
1.5A
floating, the equivalent R
2
10k, 1%
3.16k
1%
=
0.1µF
V
≅ 7mΩ
IN(MAX)
V
0.1µF
SENSE
OUT
=
5.49k
1%
2200pF
I
LOAD(MAX)
f
is the same for Channel 2.
=
V
1.5k
1%
SENSE(MIN)
100pF
20V(500kHz)
M2
+
1.8V
∆I
20k
1%
L(NOM)
4.12k
1%
SENSE
2
25.5k
22µF
50V
33pF
2.2µH
1%
L2
= 180ns
38501 F14
resistor value
=
V
7V TO
20V
IN
C
100µF
X2
V
1.8V
5A
OUT2
OUT2
38501fc