SC196AMLTRT Semtech, SC196AMLTRT Datasheet - Page 8

• Manufacturer Part Number: SC196AMLTRT
• Description: IC SYNC BUCK CONV 1.5A 10-MLP
• Manufacturer: Semtech
• Type: Step-Down (Buck)r

Specifications of SC196AMLTRT

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1V, 1.05V, 1.2V, 1.8V
• Current - Output: 1.5A
• Frequency - Switching: 1MHz
• Voltage - Input: 2.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MLP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: SC196AMLTR

Power Save Mode Operation
The PSAVE mode may be selected by tying the SYNC/
PWM pin to GND. Selecting PSAVE mode will enable the
SC196A to automatically activate/deactivate operation
at light loads, maximizing effi ciency across the full load
range. The SC196A automatically detects the load current
at which it should enter PSAVE mode. The SC196A is
optimized to track maximum effi ciency with respect to
V
In PSAVE mode, V
upper level by a switching burst. Once the upper level has
been reached, the switching is stopped and the quiescent
current is reduced. V
in this low current state as the load current discharges
the output capacitor. The burst-to-off period in PSAVE will
decrease as the load current reduces.
The PSAVE switching burst frequency is controlled so that
the inductor current ripple is similar to that in PWM mode.
The minimum switching frequency during this period is
limited to 650kHz.
The SC196A automatically detects when to exit PSAVE
mode by monitoring V
mode, the load must be increased, causing
decrease until the power save exit threshold is reached.
© 2008 Semtech Corp.
POWER MANAGEMENT
Applications Information (Cont.)
IN
.
0.7%
1.5%
V
-2%
0 A
OUT
BURST
PSAVE Mode at Light Load
Inductor Current
OFF
Power Save Operation
OUT
OUT
is driven from a lower level to an
OUT
falls from the upper to lower levels
. For the SC196A to exit PSAVE
Higher Load
Applied
Time
PWM Mode at Medium/
High Load
V
OUT
to
8
PSAVE levels are set high to minimize the undershoot
when exiting PSAVE. The lower PSAVE comparator level
is set +0.7% above V
at +1.5% above V
V
If PSAVE operation is required, then a 22μF output
capacitor must be used.
100% Duty Cycle Operation
The 100% duty cycle mode may be selected by connecting
the MODE pin high. This will allow the SC196A to maintain
output regulation under low input voltage/high output
voltage conditions.
In 100% duty cycle operation, as the input supply drops
toward the output voltage, the PMOS on-time increases
linearly above the maximum value in fi xed-frequency
operation until the PMOS is active continuously. Once
the PMOS is switched on continuously, the output voltage
tracks the input voltage minus the voltage drop across
the PMOS power device and inductor according to the
following relationship:
where,
OUT
Minimum V
.
2.95
2.85
2.75
2.9
2.8
2.7
3
0.05
V
V
I
R
R
OUT
OUT
IN
DSP
IND
V
V
IN
0.1
= Output voltage
= Input voltage
= Output current
= PMOS switch ON resistance
= Series resistance of the inductor
OUT
OUT
for Fixed Frequency Operation Vs. R
OUT
V
V
with the exit threshold at -2% below
OUT
IN
IN
Inductor DC R esistance
, and the upper comparator level
0.15
I
I
OUT
OUT
(R
(R
DSP
DSP
0.2
(
Ω
)
R
R
IND
IND
PRELIMINARY
)
)
V
0.25
OUT
I
www.semtech.com
SC196A
OUT
= 1.8V
=1A
0.3
IND