TEA1501 Philips Semiconductors, TEA1501 Datasheet - Page 10

• Manufacturer Part Number: TEA1501
• Description: Greeny; GreenChip
• Manufacturer: Philips Semiconductors

Philips Semiconductors
DESIGN EQUATIONS
Primary peak current
The primary peak current is determined by the sense
resistor R
M
The maximum drain current is 0.25 A, this results in a
minimum value for resistor R
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
I
frequency.
The switching frequency can be adjusted between
20 and 50 kHz by the reference resistor R
R
The minimum value for resistor R
maximum value is 62 k .
Leading edge blanking
The leading edge blanking time is determined by the
reference resistor R
The leading edge blanking time consists of a constant time
and a time which tracks with the period time of the switch
oscillator
1998 Aug 19
P
f
prim
R
t
switch
ANGE OF
LEB
INIMUM VALUE OF
out(max)
Greeny; GreenChip
Src
is the primary peak current and f
=
=
=
t
V
--------------- -
constant
is the efficiency, Lp is the primary inductance,
-------------------------------- -
k
Src
=
I
switch
detect
R
prim
Ref
and may be calculated as shown below:
1
VALUES
1
-- -
2
+
R
R
k
Ref
L
Ref
Src
LEB
p
as shown below:
I
prim
R
Ref
2
Src
f
of 2.0 .
switch
Ref
is 24 k , the
switch
Ref
is the switching
:
10
Burst oscillator
The power threshold for data transfer is determined by the
burst frequency, according to the following formula:
The power ratio between P
The desired P
frequency. For example, when the desired P
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 R
capacitor C
M
The minimum value for capacitor C
P
f
--------------------- -
P
handbook, halfpage
burst
data
out(max)
INIMUM VALUE OF
P
data
=
f burst
=
(Hz)
900
450
180
--------------------------------------------- -
k
0
burst
=
0
Bt
f
------------------------------ -
Fig.8 f
1
-- -
2
burst
as shown below:
data
f
R
L
switch
1
/P
Ref
p
C
N
burst
out(max)
Bt
I
data
prim
C
versus P
Bt
f switch = 50 kHz
2
0.5
ratio determines the burst
f switch = 20 kHz
data
f
burst
and P
data
Preliminary specification
N
Bt
P data /P out(max)
Ref
/P
data
out(max)
is 3.3 nF.
out(max)
and the burst
1
TEA1501
is therefore:
data
.
MGM827
/P
out(max)