LTC3728LEGN#PBF Linear Technology, LTC3728LEGN#PBF Datasheet - Page 15
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LTC3728LEGN#PBF
Manufacturer Part Number
LTC3728LEGN#PBF
Description
IC REG SW DUAL 2PH STPDWN 28SSOP
Manufacturer
Linear Technology
Series
PolyPhase®r
Type
Step-Down (Buck)r
Datasheet
1.LTC3728LXCUHPBF.pdf
(36 pages)
Specifications of LTC3728LEGN#PBF
Internal Switch(s)
No
Synchronous Rectifier
Yes
Number Of Outputs
2
Voltage - Output
0.8 ~ 7 V
Current - Output
3A
Frequency - Switching
250kHz ~ 550kHz
Voltage - Input
4.5 ~ 28 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
28-SSOP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Power - Output
-
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OPERATION
duty cycles which, in turn, are dependent upon the input
voltage V
the RMS input current varies for single-phase and 2-phase
operation for 3.3V and 5V regulators over a wide input
voltage range.
It can readily be seen that the advantages of 2-phase opera-
tion are not just limited to a narrow operating range, but
in fact extend over a wide region. A good rule of thumb
for most applications is that 2-phase operation will reduce
the input capacitor requirement to that for just one channel
operating at maximum current and 50% duty cycle.
A fi nal question: If 2-phase operation offers such an ad-
vantage over single-phase operation for dual switching
regulators, why hasn’t it been done before? The answer
is that, while simple in concept, it is hard to implement.
Constant-frequency, current mode switching regulators
require an oscillator derived slope compensation signal
to allow stable operation of each regulator at over 50%
duty cycle. This signal is relatively easy to derive in
single-phase dual switching regulators, but required the
development of a new and proprietary technique to allow
2-phase operation. In addition, isolation between the two
IN
(Duty Cycle = V
(Refer to Functional Diagram)
OUT
/V
IN
). Figure 4 shows how
channels becomes more critical with 2-phase operation
because switch transitions in one channel could potentially
disrupt the operation of the other channel.
These 2-phase parts are proof that these hurdles have
been surmounted. They offer unique advantages for the
ever expanding number of high effi ciency power supplies
required in portable electronics.
Figure 4. RMS Input Current Comparison
3.0
2.5
2.0
1.5
1.0
0.5
0
LTC3728L/LTC3728LX
0
V
V
O1
O2
= 5V/3A
= 3.3V/3A
10
INPUT VOLTAGE (V)
DUAL CONTROLLER
SINGLE PHASE
DUAL CONTROLLER
2-PHASE
20
30
3728 F04
40
15
3728lxfe