LTC3406B-2ES5#TRPBF Linear Technology, LTC3406B-2ES5#TRPBF Datasheet - Page 6

• Manufacturer Part Number: LTC3406B-2ES5#TRPBF
• Description: IC SYNC BUCK REG 600MA TSOT23-5
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3406B-2ES5#TRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 5.5 V
• Current - Output: 600mA
• Frequency - Switching: 2.25MHz
• Voltage - Input: 2.5 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: TSOT-23-5, TSOT-5, TSOP-5
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

FU CTIO AL DIAGRA
OPERATIO
LTC3406B-2
Main Control Loop
The LTC3406B-2 uses a constant frequency, current mode
step-down architecture. Both the main (P-channel
MOSFET) and synchronous (N-channel MOSFET) switches
are internal. During normal operation, the internal top power
MOSFET is turned on each cycle when the oscillator sets
the RS latch, and turned off when the current comparator,
I
which I
of error amplifier EA. When the load current increases, it
causes a slight decrease in the feedback voltage, FB, rela-
tive to the 0.6V reference, which in turn, causes the EA
amplifier’s output voltage to increase until the average
inductor current matches the new load current. While the
top MOSFET is off, the bottom MOSFET is turned on until
either the inductor current starts to reverse, as indicated by
the current reversal comparator I
the next clock cycle.
6
COMP
U
, resets the RS latch. The peak inductor current at
COMP
RUN
V
5
1
FB
resets the RS latch, is controlled by the output
U
0.6V REF
SHIFT
FREQ
U
V
OSC
IN
0.6V
SHUTDOWN
(Refer to Functional Diagram)
+
–
EA
SLOPE
COMP
0.65V
RCMP
–
+
W
OSC
, or the beginning of
OVDET
+
–
OV
RS LATCH
R
S
Q
Q
The comparator OVDET guards against transient over-
shoots >6.25% by turning the main switch off and keeping
it off until the fault is removed.
Pulse Skipping Mode Operation
At light loads, the inductor current may reach zero or re-
verse on each pulse. The bottom MOSFET is turned off by
the current reversal comparator, I
voltage will ring. This is discontinuous mode operation,
and is normal behavior for the switching regulator. At very
light loads, the LTC3406B-2 will automatically skip pulses
in pulse skipping mode operation to maintain output regu-
lation. Refer to LTC3406 data sheet if Burst Mode opera-
tion is preferred.
Short-Circuit Protection
When the output is shorted to ground, the frequency of the
oscillator is reduced to about 310kHz, 1/7 the nominal
SWITCHING
BLANKING
CIRCUIT
LOGIC
AND
–
I
SHOOT-
COMP
THRU
ANTI-
I
RCMP
+
+
–
5Ω
RCMP
, and the switch
3406B BD
4
3
2
V
sn3406b2 3406b2fs
SW
GND
IN