参数资料
型号: LTC3890EGN-1#PBF
厂商: LINEAR TECHNOLOGY CORP
元件分类: 稳压器
英文描述: SWITCHING CONTROLLER, PDSO28
封装: LEAD FREE, PLASTIC, SSOP-28
文件页数: 6/36页
文件大小: 498K
代理商: LTC3890EGN-1#PBF
LTC3890-1
14
38901f
OPERATION (Refer to the Functional Diagram)
Figure 1. Input Waveforms Comparing Single-Phase (a) and 2-Phase (b) Operation for Dual Switching Regulators
Converting 12V to 5V and 3.3V at 3A Each. The Reduced Input Ripple with the 2-Phase Regulator Allows
Less Expensive Input Capacitors, Reduces Shielding Requirements for EMI and Improves Efciency
Figure 2. RMS Input Current Comparison
together. The result is a signicant reduction in total RMS
input current, which in turn allows less expensive input
capacitors to be used, reduces shielding requirements for
EMI and improves real world operating efciency.
Figure 1 compares the input waveforms for a representative
single-phase dual switching regulator to the LTC3890-1
2-phase dual switching regulator. An actual measure-
ment of the RMS input current under these conditions
shows that 2-phase operation dropped the input current
from 2.53ARMS to 1.55ARMS. While this is an impressive
reduction in itself, remember that the power losses are
proportional to IRMS2, meaning that the actual power
wasted is reduced by a factor of 2.66. The reduced input
ripple voltage also means less power is lost in the input
power path, which could include batteries, switches,
trace/connector resistances and protection circuitry.
Improvements in both conducted and radiated EMI also
directly accrue as a result of the reduced RMS input cur-
rent and voltage.
Of course, the improvement afforded by 2-phase opera-
tion is a function of the dual switching regulator’s relative
duty cycles which, in turn, are dependent upon the input
voltage VIN (Duty Cycle = VOUT/VIN). Figure 2 shows how
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
operation are not just limited to a narrow operating range,
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.
The schematic on the rst page is a basic LTC3890-1 ap-
plication circuit. External component selection is driven
by the load requirement, and begins with the selection of
RSENSE and the inductor value. Next, the power MOSFETs
are selected. Finally, CIN and COUT are selected
IIN(MEAS) = 2.53ARMS
IIN(MEAS) = 1.55ARMS
38901 F01
5V SWITCH
20V/DIV
3.3V SWITCH
20V/DIV
INPUT CURRENT
5A/DIV
INPUT VOLTAGE
500mV/DIV
INPUT VOLTAGE (V)
0
INPUT
RMS
CURRENT
(A)
3.0
2.5
2.0
1.5
1.0
0.5
0
10
20
30
40
38901 F02
SINGLE PHASE
DUAL CONTROLLER
2-PHASE
DUAL CONTROLLER
VO1 = 5V/3A
VO2 = 3.3V/3A
相关PDF资料
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