Rainbow-electronics MAX5940B Instrukcja Użytkownika Pobierz pdf (Strona 3)

MAX5940A/MAX5940B

IEEE 802.3af PD Interface Controller

For Power-Over-Ethernet

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Note 1: All min/max limits are production tested at +85°C. Limits at +25°C and -40°C are guaranteed by design.

Note 2: The input offset current is illustrated in Figure 1.

Note 3: Effective differential input resistance is defined as the differential resistance between GND and V

without any external

resistance. See Figure 1.

Note 4: Classification current is turned off whenever the IC is in power mode.

Note 5: See Table 2 in the PD Classification Mode section. R

DISC

and R

must be ±1%, 100ppm or better. I

CLASS

includes the IC

bias current and the current drawn by R

DISC

Note 6: See the Thermal Dissipation section for details.

Note 7: When UVLO is connected to the midpoint of an external resistor-divider with a series resistance of 25.5kΩ (±1%), the turn-

on threshold set-point for the power mode is defined by the external resistor-divider. Make sure the voltage on the UVLO

pin does not exceed its maximum rating of 8V when V

is at the maximum voltage (MAX5940B only).

Note 8: When the UVLO input voltage is below V

TH,G,UVLO,

the MAX5940B sets the UVLO threshold internally.

Note 9: An input voltage or V

UVLO

glitch below their respective thresholds shorter than or equal to t

OFF_DLY

does not cause the

MAX5940A/MAX5940B to exit power-on mode (as long as the input voltage remains above an operable voltage level of 12V).

Note 10: Guaranteed by design.

Note 11: PGOOD references to OUT while PGOOD references to V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

UVLO Input Ground-Sense

Threshold (Note 8)

UVLO

50 440 mV

UVLO Input Ground-Sense Glitch

Rejection

UVLO = V

7µs

Power Turn-Off Voltage,

Undervoltage Lockout Deglitch

Time (Note 9)

OFF_DLY

, V

UVLO

falling 0.32 ms

= +25°C

(Note 10)

0.6 1.1

Isolation Switch N-Channel

MOSFET On-Resistance

Output current =

300mA, V

GATE

= 6V,

measured between

OUT and V

= +85°C 0.8 1.5

Ω

Isolation Switch N-Channel

MOSFET Off-Threshold Voltage

GSTH

OUT = GND, V

GATE

- V

EE,

output current

< 1µA

0.5 V

GATE Pulldown Switch Resistance R

Power-off mode, V

= 12V,

UVLO = V

for MAX5940B

38 80 Ω

GATE Charging Current I

GATE

= 2V 5 10 15 µA

GATE High Voltage V

GATE

= 1µA 5.59 5.76 5.93 V

OUT

- V

, |V

OUT

- V

| decreasing,

GATE

= 5.75V

1.16 1.23 1.31 V

PGOOD, PGOOD Assertion V

OUT

Threshold

OUTEN

Hysteresis 70 mV

(GATE - V

) increasing, OUT = V

4.62 4.76 4.91 V

PGOOD, PGOOD Assertion V

GATE

Threshold

GSEN

Hysteresis 80 mV

PGOOD, PGOOD Output Low

Voltage (Note 11)

OLDCDC

SINK

= 2mA; for PGOOD, OUT ≤

(GND - 5V)

0.4 V

PGOOD Leakage Current (Note 11) GATE = high, GND - V

OUT

= 67V 1 µA

PGOOD Leakage Current (Note 11) GATE = V

, PGOOD - V

= 67V 1 µA

ELECTRICAL CHARACTERISTICS (continued)

= (GND - V

) = 48V, GATE = PGOOD = PGOOD = OUT = OPEN, UVLO = V

, T

= -40°C to +85°C, unless otherwise noted.

Typical values are at T

= +25°C. All voltages are referenced to V

, unless otherwise noted.) (Note 1)

1 2 3 4 5 6 7 8 ... 14 15

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