MAX5003EEE-T Maxim Integrated Products, MAX5003EEE-T Datasheet - Page 13

• Manufacturer Part Number: MAX5003EEE-T
• Description: Voltage Mode PWM Controllers PWM Power-Supply Controller
• Manufacturer: Maxim Integrated Products

Specifications of MAX5003EEE-T

• Topology: Flyback, Forward
• Output Current: 1000 mA
• Switching Frequency: 300 KHz
• Duty Cycle (max): 75 %
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Package / Case: QSOP-16
• Mounting Style: SMD/SMT
• Synchronous Pin: Yes

Figure 3. Application Example 2: Isolated -48V to +5V Converter
where:
5) The other parameter that defines the transformer is
-36V TO -72V
DC
V
DC = Duty cycle. Set to calculated minimum duty
PWR
This gives an inductance value (L
mately 65µH.
peak current. This is given by:
The peak secondary current is the peak primary cur-
rent multiplied by the turns ratio, or 0.8A · 8 = 6.4A.
Calculating the minimum duty cycle:
With these numbers, the transformer manufacturer
can choose a core.
IN
-48V
I
0V
PRI
(
MIN
0.1µF
39k
R1
1M
R2
IN
=
)
cycle at V
= Input power, at maximum output power
=
0.1µF
L
2
PRI
DC
×
PWR
(
×
MAX
______________________________________________________________________________________
MIN.
ƒ
470nF
SW
62k
IN
)
×
=
V
V
IN MAX
IN MIN
65 H
(
(
1.3k
0.1µF
2
µ
×
)
)
×
6.25W
1
2
3
4
5
6
7
8
=
300kHz
V+
INDIV
ES
FREQ
SS
REF
CON
COMP
43
PRI
MAX5003
%
) of approxi-
MAXTON
×
PGND
AGND
=
NDRV
V
V
CS
0.8A
FB
DD
CC
36
72
16
15
14
13
12
11
10
9
V
V
10µF
=
51k
Power-Supply Controller
33µF
6) For this application, the MAX5003 must be pro-
R
100Ω
MAXTON
grammed for a maximum duty cycle of 55% at 36V.
The MAX5003 will automatically scale the limit with
the reciprocal of the input voltage as it changes. The
duty-cycle limit for an input voltage of 72V will be
27% (half of 55%). The duty cycle needed to stay out
of continuous conduction at 72V is 37%, so there is a
10% margin. The maximum duty time scales with the
voltage at the undervoltage lockout pin, V
voltage at INDIV is set by selecting the power line
undervoltage lockout trip point. The trip point for this
system, running from 36V to 72V, is 32V. Then INDIV
must be connected to the center point of a divider
with a ratio of 32/1.25, connected between the
power line and ground. Then R
IRFD620S
0.1µF
0.1Ω
65µH
R
CS
L
P
2
=
=
High-Voltage PWM



5



XFACOILTRCTX03
V
36
32
V
UVL
MIN
V
V
CMSD4448
MBRS130L
8
7



11, 12
9, 10









100
300
100
MDC217
ƒ
kHz
kHz
SW
5
6
kHz
4.7µF
22µF
7












75
55
240k
DC
22µF
%
%
TL431
1
2
MAXTON
MAX



680Ω
75
200
%
(
V
MIN
k
Ω
51Ω
3900pF
is:
=
)
0.01µF



55
INDIV
200
k
Ω
24.9k
24.9k
k
. The
+5V
1A
-
Ω
13