DAK-21A Power Integrations, DAK-21A Datasheet - Page 4

• Manufacturer Part Number: DAK-21A
• Description: KIT DESIGN ACCELERATOR DPA SW
• Manufacturer: Power Integrations
• Series: DPA-Switch®r

Specifications of DAK-21A

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Isolated
• Voltage - Output: 5V
• Current - Output: 6A
• Voltage - Input: 36 ~ 72V
• Regulator Topology: Buck
• Frequency - Switching: 400kHz
• Board Type: Fully Populated
• Utilized Ic / Part: DPA423, DPA424, DPA425, DPA426
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

DPA-Switch in PoE Applications
Power over Ethernet (PoE) is a method whereby power is transmitted to Ethernet-connected equipment (VoIP telephones, WLAN
transmitters, security cameras) from the central switch. Power Integrations has developed circuits for highly cost-effective IEE802.3af
compliant power supplies. Tested by the University of New Hampshire’s Interoperability Consortium (UNH-IOC), PI solutions have been
shown to work with all available Power Sourcing Equipment (PSE). The results of the UNH-IOC testing are shown on the PI website.
Operation: PoE Powered Device (PD) fulfi lls three functions to work in conjunction with the sending end PSE: detection, classifi cation and
undervoltage lockout.
Detection Phase: The PSE checks the PD to determine if it is PoE-enabled. During the detection phase, the PSE applies a voltage ramp
to the PD and looks for a characteristic impedance from the load (25 kΩ). If the signature impedance is detected, the PSE moves on to the
classifi cation phase. The signature identifi cation voltage is a ramp voltage between 2.5 V and 10 V. A 24.9 kΩ resistor provides the correct
signature impedance for detection.
Classifi cation Phase: The PSE continues to ramp the voltage to the PD. Between 14.5 V and 20.5 V, the PD must draw a specifi ed
current to identify the device class. The classifi cation current describes the amount of power the PD will require during normal operation. A
table of classifi cation current and operating PD power requirements is shown below.
Turn-on Phase: The PSE continues to ramp the input voltage up to 30 V. When the undervoltage lockout (UVLO) circuit is released the
PD is allowed to power up. A typical undervoltage lockout circuit is shown in the Figure above.
For additional information see Design Ideas DI-70 (www.powerint.com/PDFFiles/di70.pdf) & DI-88 (www.powerint.com/PDFFiles/di88.pdf),
also Reference Design Kits DAK-68A and DAK-86.
4 DC-DC Product Selector Guide | September 2008
Classifi cation Power Levels
Table 1.
Class
0
1
2
3
4
Classifi cation Power Levels.
Reserved
Power
0.44 W
0.44 W
3.84 W
6.49 W
(Min)
DPA-Switch – Constant Current LED Driver (10 W, 500 mA)
24 V - 200 V
Reserved
12.95 W
12.95 W
Power
3.84 W
6.49 W
(Max)
RTN
DC
Class
17 mA
26 mA
36 mA
(Min)
0 mA
9 mA
SL23
D1
1 μF
50 V
C4
(Max)
12 mA
20 mA
30 mA
44 mA
I
4 mA
CLASS
392 kΩ
1%
R3
WHITE
WHITE
WHITE
10 kΩ
D9
D4
D5
1%
R4
D
S
100 μH
CONTROL
L1
X
L
WHITE
WHITE
WHITE
DPA-Switch
D7
D8
D6
F
PoE Class 0 Interface with MOSFET Pass-Switch
DPA423
Figure 1.
220 nF
25 V
U1
C
C1
470 pF
50 V
C6
10 μF
25 V
C2
PoE Class 0 Interface Circuit Using a MOSFET Pass-Switch.
DPA-Switch can support
long strings of up to 50 LEDs
(assuming V
2.2 kΩ
2.2 kΩ
R1
24.9 kΩ/1%
R7
1/4 W
f
10 μF
R51
25 V
= 3.6 V)
C3
PI-4564-080307
MA2J11300L
MA2J11
300L
10 nF
D3
50 V
D2
C5
51 kΩ
1/8 W
R52
PI-3825-072205