MAX5022EVKIT Maxim Integrated Products, MAX5022EVKIT Datasheet - Page 4

• Manufacturer Part Number: MAX5022EVKIT
• Description: EVAL KIT FOR MAX5022
• Manufacturer: Maxim Integrated Products

Specifications of MAX5022EVKIT

• Main Purpose: AC/DC, Primary Side
• Outputs And Type: 1, Isolated
• Power - Output: 5W
• Voltage - Output: 5V
• Current - Output: 1A
• Voltage - Input: 85 ~ 265VAC
• Regulator Topology: Flyback
• Frequency - Switching: 262kHz
• Board Type: Fully Populated
• Utilized Ic / Part: MAX5022
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

MAX5022 Evaluation Kit
The MAX5022 EV kit is an off-line 5W flyback converter,
configured for +5VDC/1A output. A tertiary winding
from the transformer is used to power the device during
normal operation. The secondary winding provides the
+5VDC output and can supply up to 1A.
This EV kit uses the MAX5022, a SOT23, current-mode,
pulse width modulating (PWM) controller. This PWM
controller varies the duty cycle to compensate for the
variation in VIN and the output load to maintain a con-
stant output voltage. The duty cycle determines the
on/off duration of the MOSFET (N1). The n-channel
MOSFET is used as a switch to control the current
through the primary winding of the transformer (T1).
4
Figure 1. Efficiency Graph
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90
80
70
60
50
40
30
20
10
0
0 100 200 300 400 500 600 700 800 900 1000
MAX5022 EFFICIENCY
OUTPUT CURRENT (mA)
Detailed Description
V
V
V
IN
IN
IN
= 85VAC
= 120VAC
= 265VAC
The duty cycle is controlled by the feedback loop con-
sisting of voltage-divider resistors (R4, R5), a shunt regu-
lator (U3), an optocoupler (U2), and the PWM compara-
tor inside the MAX5022. This network provides the isolat-
ed feedback, regulating the output voltage to 5V ±2%
with up to 4500VDC input-to-output isolation.
The MAX5022 senses the current going through the
transformer’s primary winding with a current-sense
resistor (R7), and shuts down the output when the out-
put current exceeds the current limit of 1.6A. The
MAX5022 EV kit is protected against catastrophic fail-
ure with the fuse (F1).