LTM4601A LINER [Linear Technology], LTM4601A Datasheet - Page 13

• Manufacturer Part Number: LTM4601A
• Description: Ultralow EMI 28VIN, 6A DC/DC ?Module Regulator
• Manufacturer: LINER [Linear Technology]

applicaTions inForMaTion
Fault Conditions: Current Limit and Overcurrent
Foldback
LTM4606 has a current mode controller, which inher-
ently limits the cycle-by-cycle inductor current not only
in steady-state operation, but also in transient.
To further limit current in the event of an overload condi-
tion, the LTM4606 provides foldback current limiting. If the
output voltage falls by more than 50%, then the maximum
output current is progressively lowered to about one sixth
of its full current limit value.
Soft-Start and Tracking
The TRACK/SS pin provides a means to either soft-start
the regulator or track it to a different power supply.
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
0.1 0.15 0.2 0.25
Figure 3. Normalized Output Ripple Current vs Duty Cycle, Dlr = V
0.3
0.35
0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9
DUTY CYCLE (V
A capacitor on this pin will program the ramp rate of the
output voltage. A 1.5µA current source will charge up the
external soft-start capacitor to 80% of the 0.6V internal
voltage reference plus or minus any margin delta. This will
control the ramp of the internal reference and the output
voltage. The total soft-start time can be calculated as:
When the RUN pin falls below 2.5V, then the SS pin is reset
to allow for proper soft-start control when the regulator is
enabled again. Current foldback and force continuous mode
are disabled during the soft-start process. The soft-start
function can also be used to control the output ramp up
time, so that another regulator can be easily tracked to it.
O
/V
IN
t
SOFTSTART
)
≅ 0.8 • 0.6V ± V
1-PHASE
2-PHASE
3-PHASE
4-PHASE
6-PHASE
(
4612 F05
O
T/L
I
OUT(MARGIN)
LTM4606
)
•
1.5µA
C
13
SS
4606fb