參數(shù)資料
型號: LT1576I
廠商: Linear Technology Corporation
英文描述: CAP 220UF 25V ELECT TG SMD
中文描述: 1.5A的,200kHz降壓型開關(guān)穩(wěn)壓器
文件頁數(shù): 24/28頁
文件大?。?/td> 290K
代理商: LT1576I
24
LT1576/LT1576-5
APPLICATIO
S I
FOR
ATIO
U
with large inductors. Output ripple voltage for the positive-
to-negative converter will be much higher than a buck
converter. Ripple current in the output capacitor will also
be much higher. The following equations can be used to
calculate operating conditions for the positive-to-negative
converter.
Maximum load current:
( )(
+
(
+
(
I
P
= Maximum rated switch current
V
IN
= Minimum input voltage
V
OUT
= Output voltage
V
F
= Catch diode forward voltage
0.35 = Switch voltage drop at 1.5A
Example: with V
IN(MIN)
= 5.5V, V
OUT
= 5V, L = 30
μ
H,
V
F
= 0.5V, I
P
= 1.5A: I
MAX
= 0.6A. Note that this equation
does not take into account that maximum rated switch
current (I
P
) on the LT1576 is reduced slightly for duty
cycles above 50%. If duty cycle is expected to exceed 50%
(input voltage less than output voltage), use the actual I
P
value from the Electrical Characteristics table.
Operating duty cycle:
W
U
U
I
I
V
V
V
V
f L
V
V
V
V
V
V
MAX
P
IN
OUT
OUT
IN
OUT
IN
OUT
IN
OUT
F
=
)
)( )( )
0 35
)
(
)
(
)
+
(
)
2
0 35
.
.
DC
V
0 3
.
V
V
V
V
OUT
F
IN
OUT
F
=
+
+
+
(This formula uses an average value for switch loss, so it
may be several percent in error.)
With the conditions above:
DC
=
+
.
+ +
5
=
5
0 3
0 5
.
5 5
.
0 5
.
51
%
This duty cycle is close enough to 50% that I
P
can be
assumed to be 1.5A.
OUTPUT DIVIDER
If the adjustable part is used, the resistor connected to
V
OUT
(R2) should be set to approximately 5k. R1 is
calculated from:
(
R
R V
OUT
2
1
1 21
1 21
=
)
INDUCTOR VALUE
Unlike buck converters, positive-to-negative converters
cannot use large inductor values to reduce output ripple
voltage. At 200kHz, values larger than 75
μ
H make almost
no change in output ripple. The graph in Figure 16 shows
peak-to-peak output ripple voltage for a 5V to –5V con-
verter versus inductor value. The criteria for choosing the
INDUCTOR SIZE (
μ
H)
0
O
P
)
150
120
90
60
30
0
60
1576 F16
15
30
45
75
DISCONTINUOUS
I
LOAD
= 0.25A
DISCONTINUOUS
I
LOAD
= 0.1A
5V TO –5V CONVERTER
OUTPUT CAPACITOR’S
ESR = 0.1
CONTINUOUS
I
LOAD
> 0.38A
Figure 16. Ripple Voltage on Positive-to-Negative Converter
相關(guān)PDF資料
PDF描述
LT1576IS8-5 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
LT1576IS8-SYNC MM,62.5M,BREAKOUT STYLE BULK FO CBL - 24FIBER 100
LT1576CS8-5SYNC MM,62.5M,DIST STYLE,BULK FO CABLE - 4FIB 500FT
LT1576IS8-5SYNC MM,62.5M,DIST STYLE,BULK FO CABLE - 12FIB 1000FT
LT1576IS8 RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS
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