MAX5981AETE+ Maxim Integrated Products, MAX5981AETE+ Datasheet - Page 11

• Manufacturer Part Number: MAX5981AETE+
• Description: Power Switch ICs - POE / LAN IEEE 802.3af/at PDIC Controller
• Manufacturer: Maxim Integrated Products

Specifications of MAX5981AETE+

• Lead Free Status / Rohs Status: Details

Depending on the input voltage (V
MAX5981 operates in four differ ent modes: PD detec-
tion, PD classification, mark event, and PD power. The
devices enter PD detection mode when the input voltage
is between 1.4V and 10.1V. The device enters PD clas-
sification mode when the input voltage is between 12.6V
and 20V. The device enters PD power mode once the
input voltage exceeds V
In detection mode, the power source equipment (PSE)
applies two voltages on V
range (1V step minimum) and then records the current
measure ments at the two points. The PSE then computes
DV/DI to ensure the presence of the 24.9kI signature
resistor. Connect the signature resistor (R
to DET for proper signature detection. The MAX5981
pulls DET low in detection mode. DET goes high imped-
ance when the input voltage exceeds 12.5V. In detection
mode, most of the MAX5981 internal circuitry is off and
the offset current is less than 10µA.
If the voltage applied to the PD is reversed, install pro-
tection diodes at the input terminal to prevent internal
damage to the MAX5981 (see the Typical Application
Circuit). Since the PSE uses a slope technique (DV/DI) to
calculate the signature resistance, the DC offset due to
the protection diodes is subtracted and does not affect
the detection process.
In the classification mode, the PSE classifies the PD
based on the power consumption required by the PD.
Table 1. Setting Classification Current
*V
IEEE 802.3af/at-Compliant, Powered Device Interface
CLASS
IN
is measured across the MAX5981A/MAX5981B input V
0
1
2
3
4
5
POWER USED
0.44 to 12.95
6.49 to 12.95
12.95 to 25.5
0.44 to 3.84
3.84 to 6.49
MAXIMUM
Classification Mode (12.6V P V
BY PD
> 25.5
______________________________________________________________________________________
(W)
Detection Mode (1.4V P V
Detailed Description
Controllers with
ON
.
IN
R
66.5
43.7
30.9
21.3
615
117
in the 1.4V to 10.1V
(I)
CLS
Operating Modes
IN
= V
DET
DD
12.6 to 20
12.6 to 20
12.6 to 20
12.6 to 20
12.6 to 20
12.6 to 20
V
(V)
IN
) from V
- V
IN
IN
*
P 10.1V)
SS
P 20V)
), the
DD
DD
CLASS CURRENT SEEN AT
to V
MIN
Integrated Power MOSFET
17
26
36
54
SS
0
9
This allows the PSE to efficiently manage power distribu-
tion. Class 0–5 is defined as shown in Table 1. (The IEEE
802.3af/at standard defines only Class 0–4 and Class 5
for any spe cial requirement.) An external resistor (R
connected from CLS to V
The PSE determines the class of a PD by applying a volt-
age at the PD input and measuring the current sourced
out of the PSE. When the PSE applies a voltage between
12.6V and 20V, the MAX5981A/MAX5981B exhibit a cur-
rent characteristic with a value shown in Table 1. The
PSE uses the classification current informa tion to classify
the power requirement of the PD. The classification cur-
rent includes the current drawn by R
current of the MAX5981A/MAX5981B so the total current
drawn by the PD is within the IEEE 802.3af/at standard
figures. The classification current is turned off whenever
the device is in power mode.
During 2-Event classification, a Type 2 PSE probes PD
for classification twice. In the first classification event,
the PSE presents an input voltage between 12.6V and
20.5V and the MAX5981A/MAX5981B pres ent the pro-
grammed load I
voltage below the mark event threshold of 10.1V and
the MAX5981A/MAX5981B pres ent the mark current
(I
When the MAX5981A/MAX5981B are pow ered by a Type
2 PSE, the 2-Event identification output 2EC asserts low
after the internal isolation n-channel MOSFET is fully
turned on. 2EC current sink is turned off when V
below the UVLO threshold (V
V
V
.
MARK
DD
DD
V
IN
goes below VTHR to reset the latched output of the
goes above the UVLO threshold (V
). This sequence is repeated one more time.
(mA)
MAX
12
20
30
44
64
4
CLASS
2-Event Classification and Detection
. The PSE then drops the probing
SS
CLASSIFICATION CURRENT
sets the classification current.
SPECIFICATION (mA)
MIN
OFF
16
25
35
51
0
8
IEEE 802.3at PD
) and turns on when
CLS
and the supply
ON
MAX
13
21
31
45
68
), unless
5
DD
goes
CLS
11
)