LTC3890EGN-1#PBF Linear Technology, LTC3890EGN-1#PBF Datasheet - Page 20

• Manufacturer Part Number: LTC3890EGN-1#PBF
• Description: IC BUCK SYNC ADJ 25A DUAL 28SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3890EGN-1#PBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.8 ~ 24 V
• Current - Output: 25A
• Frequency - Switching: 50kHz ~ 900kHz
• Voltage - Input: 4 ~ 60 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Primary Input Voltage: 12V
• No. Of Outputs: 2
• Output Voltage: 24V
• Output Current: 25A
• No. Of Pins: 32
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 1 - Unlimited
• Supply Voltage Min: 4V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

Alternatively, the TRACK/SS pin can be used to track two
(or more) supplies during start-up, as shown qualitatively
in Figures 7a and 7b. To do this, a resistor divider should
be connected from the master supply (V
SS pin of the slave supply (V
During start-up V
set by the resistor divider:
For coincident tracking (V
LTC3890
Tracking and Soft-Start (TRACK/SS Pins)
The start-up of each V
the respective TRACK/SS pin. When the voltage on the
TRACK/SS pin is less than the internal 0.8V reference,
the LTC3890 regulates the V
on the TRACK/SS pin instead of 0.8V. The TRACK/SS pin
can be used to program an external soft-start function
or to allow V
Soft-start is enabled by simply connecting a capacitor
from the TRACK/SS pin to ground, as shown in Figure 6.
An internal 1μA current source charges the capacitor,
providing a linear ramping voltage at the TRACK/SS pin.
The LTC3890 will regulate the V
according to the voltage on the TRACK/SS pin, allowing
V
The total soft-start time will be approximately:
APPLICATIONS INFORMATION
20
OUT
R
R
t
V
SS
A
B
Figure 6. Using the TRACK/SS Pin to Program Soft-Start
V
OUT
to rise smoothly from 0V to its final regulated value.
X
= R
= R
= C
=
TRACKA
TRACKB
SS
R
OUT
TRACKA
•
R
0.8V
A
1μA
to track another supply during start-up.
OUT
•
will track V
OUT
R
C
SS
TRACKA
OUT
is controlled by the voltage on
TRACK/SS
SGND
1/2 LTC3890
FB
R
OUT
= V
A
pin voltage to the voltage
+ R
FB
+ R
), as shown in Figure 8.
X
3890 F06
X
according to the ratio
pin (and hence V
during start-up):
TRACKB
B
X
) to the TRACK/
OUT
)
Figure 7. Two Different Modes of Output Voltage Tracking
Figure 8. Using the TRACK/SS Pin for Tracking
R
R
TRACKB
TRACKA
(7b) Ratiometric Tracking
(7a) Coincident Tracking
V
x
V
TIME
TIME
OUT
R
R
B
A
V
TRACK/SS
1/2 LTC3890
FB
3890 F07a
3890 F07b
3890 F08
V
V
V
V
X(MASTER)
OUT(SLAVE)
X(MASTER)
OUT(SLAVE)
3890fa