參數(shù)資料
型號(hào): LT3509IDE#TRPBF
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: 1.2 A DUAL SWITCHING CONTROLLER, 2500 kHz SWITCHING FREQ-MAX, PDSO14
封裝: 4 X 3 MM, LEAD FREE, PLASTIC, MO-229WGED-3, DFN-14
文件頁數(shù): 9/24頁
文件大?。?/td> 271K
代理商: LT3509IDE#TRPBF
LT3509
17
3509fc
and Z5U types lose a large fraction of their capacitance
with applied voltage and at temperature extremes. Because
loop stability and transient response depend on the value
of COUT, this loss may be unacceptable. Use X7R and X5R
types.
The value of the output capacitor greatly affects the
transient response to a load step. It has to supply extra
current demand or absorb excess current delivery until
the feedback loop can respond. The loop response is
dependent on the error amplier transconductance, the
internal compensation capacitor and the feedback net-
work. Higher output voltages necessarily require a larger
feedback divider ratio. This will also reduce the loop gain
and slow the response time. Fortunately this effect can be
mitigated by use of a feed-forward capacitor, CPL, across
the top feedback resistor. The small-signal model shown
in Figure 10 can be used to model this in a simulator or
to give insight to an empirical design. Figure 11 shows
some load step responses with differing output capacitors
and CPL combinations.
Input Capacitor
The input capacitor needs to supply the pulses of charge
demanded during the on time of the switches. Little total
capacitance is required as a few hundred millivolts of ripple
at the VIN pin will not cause any problems to the device.
When operating at 2MHz and 12V, 2μF will work well. At
the lowest operating frequency and/or at low input voltages
a larger capacitor such as 4.7μF is preferred.
APPLICATIONS INFORMATION
ILOAD
700mA
300mA
VOUT (AC)
50mV/DIV
ILOAD
700mA
300mA
VOUT (AC)
50mV/DIV
TIME 20μs/DIV
3509 F11
COUT = 10μF
CPL = 0
COUT = 10μF
CPL = 82pF
Figure 11. Transient Load Response with Different Combinations
of COUT and CPL Load Current Step from 300mA to 700mA
R1 = 10k, R2 = 32.4k, VIN = 12V, VOUT = 3.3V, fSW = 2.0MHz
相關(guān)PDF資料
PDF描述
LT3509IDE#PBF 1.2 A DUAL SWITCHING CONTROLLER, 2500 kHz SWITCHING FREQ-MAX, PDSO14
LT3509EDE#PBF 1.2 A DUAL SWITCHING CONTROLLER, 2500 kHz SWITCHING FREQ-MAX, PDSO14
LT3509EDE#TRPBF 1.2 A DUAL SWITCHING CONTROLLER, 2500 kHz SWITCHING FREQ-MAX, PDSO14
LT3570EFE#TRPBF 3.1 A SWITCHING REGULATOR, 2750 kHz SWITCHING FREQ-MAX, PDSO20
LT3570IUF#PBF 3.1 A SWITCHING REGULATOR, 2750 kHz SWITCHING FREQ-MAX, PQCC24
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