SC414MLTRT Semtech, SC414MLTRT Datasheet - Page 15

• Manufacturer Part Number: SC414MLTRT
• Description: IC BUCK SYNC ADJ 6A 28MLPQ
• Manufacturer: Semtech
• Series: SmartDrive™r
• Type: Step-Down (Buck)r

Specifications of SC414MLTRT

• Mfg Application Notes: SC414 Basic Design Procedure
• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.75 ~ 5.5 V
• Current - Output: 6A
• Frequency - Switching: 200kHz ~ 1MHz
• Voltage - Input: 3 ~ 28 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-MLPQ
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: SC414MLTR

Applications Information (continued)
This method automatically produces an on-time that is
proportional to V
Under steady-state conditions, the switching frequency
can be determined from the on-time by the following
equation.
The SC414/SC424 uses an external resistor to set the on-
time which indirectly sets the frequency. The on-time can
be programmed to provide an operating frequency from
200kHz to 1MHz using a resistor between the TON pin and
ground. The resistor value is selected by the following
equation.
The maximum R
ing equation.
Immediately after the on-time, the DL (drive signal for the
low side FET) output drives high to turn on the low-side
MOSFET. DL has a minimum high time of ~320ns, after
which DL continues to stay high until one of the following
occurs:
TON limitations and V5V Supply Voltage
For V5V below 4.5V, the TON accuracy may be limited by
the input voltage.
The original RTON equation is accurate if V
below relation over the entire V
If V
range, the RTON equation is not accurate. In all cases
where V
modifi ed as follows.
•
•
IN
V
R
R
f
SW
exceeds (V5V - 1.6V) x 10, for all or part of the V
VFB falls below the 750mV reference
The Zero Cross Detector senses that the voltage
on the LX node is below ground. Power Save is
activated when a zero crossing is detected.
IN
TON
TON
IN
< (V5V - 1.6V) x 10
_
> (V5V - 1.6V) x 10, the RTON equation must be
T
MAX
ON
25
V
OUT
pF
V
10
TON
IN
1
V
OUT
f
IN
value allowed is shown by the follow-
SW
1
_
5 .
MIN
and inversely proportional to V
400
A
IN
V
range:
V
OUT
IN
IN
satisfi es the
IN
IN
.
Note that when V
is fi xed and does not vary with V
condition, the switching frequency will vary inversely with
V
V
The switcher output voltage is regulated by comparing
V
internal 750mV reference voltage (see Figure 3).
Note that this control method regulates the valley of the
output ripple voltage, not the DC value. The DC output
voltage V
following equation.
When a large capacitor is placed in parallel with R1 (C
V
Where ω is the angular switching frequency.
Enable and Power-save Inputs
The EN/PSV and ENL inputs are used to enable or disable
the switching regulator and the LDO. When EN/PSV is low
(grounded), the switching regulator is off and in its lowest
power state. When off , the output of the switching regula-
tor soft-discharges the output into a 10Ω internal resistor
via the VOUT pin. When EN/PSV is allowed to fl oat, the pin
voltage will fl oat to 33% of the voltage at V5V. The switch-
ing regulator turns on with power-save disabled and all
switching is in forced continuous mode. For V5V < 4.5V, it
V
IN
OUT
OUT
OUT
OUT
R
rather than approximating a fi xed frequency.
V
as seen through a resistor divider at the FB pin to the
is shown by the following equation.
TON
OUT
Voltage Selection
. 0
V
OUT
OUT
Figure 3 — Output Voltage Selection
75
. 0
25pF
is off set by the output ripple according to the
75
1
1
IN
1
f
R
R
SW
> (V5V - 1.6V) x 10 , the actual on-time
1
2
R
R
1
2
400
R
V
1
RIPPLE
V
2
RIPPLE
R
2
2
(V5V
IN
. When operating in this
SC414/SC424
1
V
1.6V)
1
OUT
R
R
2
R (
2
To FB pin
1
R
R
1
1
10
C
TOP
C
TOP
)
2
TOP
15
2
)