參數(shù)資料
型號: SA57250-33GW-G
廠商: NXP SEMICONDUCTORS
元件分類: 穩(wěn)壓器
英文描述: 0.3 A SWITCHING REGULATOR, 57.5 kHz SWITCHING FREQ-MAX, PDSO5
封裝: 1.50 MM, PLASTIC, MO-178, SOT-25, SOT-23, SOP-5
文件頁數(shù): 2/18頁
文件大?。?/td> 276K
代理商: SA57250-33GW-G
Philips Semiconductors
Product data
SA57250-XX
CMOS switching regulator (PWM controlled)
2003 Nov 12
10
APPLICATION INFORMATION
The SA57250-XX can be used for a simple boost (step-up)
converter or the less commonly used flyback converter (isolated
boost). The major operating restriction of the simple boost converter
is that its output voltage must always be above the highest
expected value of the input voltage. The flyback converter circuit
requires more parts, but the output voltage is not restricted by the
input voltage.
Boost converter fundamentals
The boost or step-up converter is a non-dielectrically isolated
switching power supply topology (arrangement of power parts). That
is, the input power source is directly connected to the output load
(ground and signals). A typical boost converter with optional passive
snubber can be seen in Figure 25.
To understand the boost converter’s operation, examine its three
periods of operation. These periods are: the power switch on-time
(period 1); the inductor discharge period (period 2); and the inductor
empty state (period 3). These periods and their associated currents
can be seen in Figure 26.
SL01466
D
VIN
CIN
ON/OFF
GND
SA57250-XX
SW
FB
PASSIVE SNUBBER
(OPTIONAL)
VOUT
COUT
L0
Figure 25. Boost converter.
SL01464
SWITCH
VOLTAGE
(V)
INDUCTOR
CURRENT
(A)
0
VIN
(VIN – VOUT)
Ipeak
ISW × RDS(ON)
CORE EMPTY,
PARASITIC CIRCULATING ENERGY
+VOUT
ENERGY BEING TRANSFERRED TO OUTPUT
SPIKE
ENERGY BEING
STORED IN INDUCTOR
+VIN
L0
PERIOD 1
PERIOD 2
PERIOD 3
Figure 26. Boost converter waveforms (discontinuous mode).
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