SC414MLTRT Semtech, SC414MLTRT Datasheet - Page 16

• 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)
is recommended to force 33% of the V5V voltage on the
EN/PSV pin to operate in forced continuous mode.
When EN/PSV is high (above 45% of the voltage at V5V)
for SC414, the switching regulator turns on with ultrasonic
power-save enabled. The SC414 ultrasonic power-save
operation maintains a minimum switching frequency of
25kH z, for applications with stringent audio
requirements.
When EN/PSV is high (above 45% of the voltage at V5V)
for SC424, the switching regulator turns on with power-
save enabled. The SC424 power-save operation is designed
to maximize effi ciency at light loads with no minimum
frequency limits. This makes the SC424 an excellent choice
for portable and battery-operated systems.
The ENL input is used to control the internal LDO. This
input provides a second function by acting as a V
sensor for the switching regulator. When ENL is low
(grounded), the LDO is off . When ENL is a logic high but
below the V
is on and the switcher is off . When ENL is above the V
UVLO threshold, the LDO is enabled and the switcher is
also enabled if the EN/PSV pin is not grounded.
Forced Continuous Mode Operation
The SC414/SC424 operates the switcher in Forced
Continuous Mode (FCM) by fl oating the EN/PSV pin (see
Figure 4). In this mode of operation, the MOSFETs are
turned on alternately to each other with a short dead time
between them to avoid cross conduction. This feature
results in uniform frequency across the full load range
with the trade-off being poor effi ciency at light loads due
to the high-frequency switching of the MOSFETs.
For V5V < 4.5V, it is recommended to force 33% of the V5V
voltage on the EN/PSV pin to operate in forced continuous
mode.
IN
UVLO threshold (2.6V typical), then the LDO
IN
ULVO
IN
Ultrasonic Power-save Operation (SC414)
The SC414 provides ultrasonic power-save operation at
light loads, with the minimum operating frequency fi xed
at slightly under 25kHz. This is accomplished by using an
internal timer that monitors the time between consecu-
tive high-side gate pulses. If the time exceeds 40μs, DL
drives high to turn the low-side MOSFET on. This draws
current from V
and V
next DH (the drive signal for the high side FET) on-time is
triggered. After the on-time is completed the high-side
MOSFET is turned off and the low-side MOSFET turns on.
The low-side MOSFET remains on until the inductor
current ramps down to zero, at which point the low-side
MOSFET is turned off .
Voltage (V
DH
DL
Inductor
Current
FB Ripple
Figure 4 — Forced Continuous Mode Operation
FB
to fall. When V
DL remains high until V
FB
)
DL drives high when on-time is completed.
OUT
through the inductor, forcing both V
On-time
(T
ON
FB
)
drops to the 750mV threshold, the
V
DH on-time is triggered when
FB
FB
reaches the FB Threshold.
falls to the FB threshold.
SC414/SC424
DC Load Current
FB threshold
(750mV)
OUT
16