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參數(shù)資料
| 型號(hào)： | 935256880112 |
| 廠商： | NXP SEMICONDUCTORS |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.25 A SWITCHING REGULATOR, 50 kHz SWITCHING FREQ-MAX, PDIP8 |
| 封裝： | SOT-97, DIP-8 |
| 文件頁數(shù)： | 2/22頁 |
| 文件大小： | 154K |
| 代理商： | 935256880112 |
1998 Aug 19
10
Philips Semiconductors
Preliminary specication
Greeny; GreenChip
TEA1501
DESIGN EQUATIONS
Primary peak current
The primary peak current is determined by the sense
resistor RSrc and may be calculated as shown below:
MINIMUM VALUE OF RSrc
The maximum drain current is 0.25 A, this results in a
minimum value for resistor RSrc of 2.0 .
Switch oscillator
The maximum output power of the converter is a function
of the switching frequency, provided that the converter
operates in discontinuous conduction mode.
Where
η is the efficiency, Lp is the primary inductance,
Iprim is the primary peak current and fswitch is the switching
frequency.
The switching frequency can be adjusted between
20 and 50 kHz by the reference resistor RRef:
RANGE OF RRef VALUES
The minimum value for resistor RRef is 24 k, the
maximum value is 62 k
.
Leading edge blanking
The leading edge blanking time is determined by the
reference resistor RRef as shown below:
The leading edge blanking time consists of a constant time
and a time which tracks with the period time of the switch
oscillator
R
Src
V
detect
I
prim
----------------
=
P
out(max)
η
1
2
---
L
p
I
prim
2
f
switch
×
=
f
switch
1
k
switch
R
Ref
×
---------------------------------
=
t
LEB
t
constant
k
LEB
R
Ref
×
()
+
=
Burst oscillator
The power threshold for data transfer is determined by the
burst frequency, according to the following formula:
The power ratio between Pdata and Pout(max) is therefore:
The desired Pdata/Pout(max) ratio determines the burst
frequency. For example, when the desired Pdata/Pout(max)
ratio is 0.5 then the burst frequency has to be 450 Hz at
50 kHz switching frequency. The burst frequency can be
adjusted by the reference resistor RRef and the burst
capacitor CBt as shown below:
MINIMUM VALUE OF CBt
The minimum value for capacitor CBt is 3.3 nF.
P
data
η
1
2
---
L
p
I
prim
2
f
burst
N
data
×
=
P
data
P
out(max)
----------------------
f
burst
N
data
×
f
switch
-------------------------------
=
f
burst
1
k
burst
R
Ref
C
Bt
×
----------------------------------------------
=
Fig.8 fburst versus Pdata/Pout(max).
handbook, halfpage
MGM827
fburst
(Hz)
fswitch = 20 kHz
fswitch = 50 kHz
450
180
900
0
0.5
1
Pdata/Pout(max)
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