LTC3406B-2ES5#PBF Linear Technology, LTC3406B-2ES5#PBF Datasheet - Page 7

• Manufacturer Part Number: LTC3406B-2ES5#PBF
• Manufacturer: Linear Technology

Specifications of LTC3406B-2ES5#PBF

• Dc To Dc Converter Type: Step Down
• Pin Count: 5
• Input Voltage: 5.5V
• Output Voltage: 0.6 to 5.5V
• Switching Freq: 2.7MHz
• Output Current: 600mA
• Efficiency: 96%
• Package Type: TSOT-23
• Output Type: Adjustable
• Switching Regulator: Yes
• Load Regulation: 0.5%
• Line Regulation: 0.4%/V
• Mounting: Surface Mount
• Input Voltage (min): 2.5V
• Operating Temperature Classification: Industrial
• Number Of Outputs: 1
• Lead Free Status / RoHS Status: Compliant

OPERATIO
frequency. This frequency foldback ensures that the in-
ductor current has more time to decay, thereby preventing
runaway. The oscillator’s frequency will progressively
increase to 2.25MHz when V
Dropout Operation
As the input supply voltage decreases to a value approach-
ing the output voltage, the duty cycle increases toward the
maximum on-time. Further reduction of the supply voltage
forces the main switch to remain on for more than one cycle
until it reaches 100% duty cycle. The output voltage will then
be determined by the input voltage minus the voltage drop
across the P-channel MOSFET and the inductor.
TO 5.5V
2.7V
V
IN
Figure 1a. High Efficiency Step-Down Converter
C
4.7µF
CER
100
90
80
70
60
50
40
30
20
10
IN
**
0.1
Figure 1b. Efficiency vs Load Current
**
*
†
MURATA LQH32CN2R2M33
TAIYO YUDEN JMK212BJ475MG
TAIYO YUDEN JMK316BJ106ML
V
T
OUT
A
V
= 25°C
IN
V
U
= 1.8V
IN
= 3.6V
V
RUN
LTC3406B-2
IN
= 4.2V
OUTPUT CURRENT (mA)
1
(Refer to Functional Diagram)
GND
V
SW
FB
V
IN
10
FB
= 2.7V
rises above 0V.
2.2µH*
22pF
100
3406B F01b
1M
1000
499k
3406B F01a
C
10µF
CER
OUT
†
V
1.8V
600mA
OUT
An important detail to remember is that at low input supply
voltages, the R
(see Typical Performance Characteristics). Therefore, the
user should calculate the power dissipation when the
LTC3406B-2 is used at 100% duty cycle with low input
voltage (See Thermal Considerations in the Applications
Information section).
Low Supply Operation
The LTC3406B-2 will operate with input supply voltages as
low as 2.5V, but the maximum allowable output current is
reduced at this low voltage. Figure 2 shows the reduction
in the maximum output current as a function of input
voltage for various output voltages.
Slope Compensation and Inductor Peak Current
Slope compensation provides stability in constant fre-
quency architectures by preventing subharmonic oscilla-
tions at high duty cycles. It is accomplished internally by
adding a compensating ramp to the inductor current
signal at duty cycles in excess of 40%. Normally, this
results in a reduction of maximum inductor peak current
for duty cycles > 40%. However, the LTC3406B-2 uses a
patent-pending scheme that counteracts this compensat-
ing ramp, which allows the maximum inductor peak
current to remain unaffected throughout all duty cycles.
Figure 2. Maximum Output Current vs Input Voltage
1200
1000
800
600
400
200
0
2.5
V
V
OUT
OUT
DS(ON)
3.0
= 1.8V
= 1.5V
SUPPLY VOLTAGE (V)
3.5
of the P-channel switch increases
V
OUT
4.0
= 2.5V
4.5
LTC3406B-2
5.0
3406B F02
5.5
sn3406b2 3406b2fs
7