MAX5945 datasheet(18/44 Pages) MAXIM

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The MAX5945 also features three other undervoltage

and overvoltage interrupts: VEE undervoltage interrupt

(VEEUV), VDD undervoltage interrupt (VDDUV), and VDD

overvoltage interrupt (VDDOV). A fault latches into the

supply events register (Table 11) but the MAX5945 does

not shut down the ports with a VEEUV, VDDUV, or VDDOV.

DC Disconnect Monitoring

Setting R13h[DCD_EN_] bits high enable DC load mon-

itoring during a normal powered state. If SENSE_ falls

below the DC load disconnect threshold, VDCTH, for

more than tDISC, the device turns off power and asserts

the LD_DISC_ bit of the corresponding port. tDISC is

programmable using R16h[0-1] and R27h[0-3].

AC Disconnect Monitoring

The MAX5945 features AC load disconnect monitoring.

Connect an external sine wave to OSC_IN. The oscilla-

tor requirements are:

•

Frequency x VP-P = 200VP-P x Hz ±15%

•

Positive peak voltage > +2V

•

Frequency > 60Hz

•

A 100Hz ±10%, 2VP-P ±5%, with +1.2V offset

(VPEAK = +2.2V, typ) is recommended.

The MAX5945 buffers and amplifies 3x the external

oscillator signal and sends the signal to DET_, where

the sine wave is AC coupled to the output. The

MAX5945 senses the presence of the load by monitor-

ing the amplitude of the AC current returned to DET_

(see the Functional Diagram).

Setting R13h[ACD_EN_] bits high enable AC load dis-

connect monitoring during the normal powered state. If

the AC current peak at the DET_ pin falls below IACTH

for more than tDISC, the device turns off power and

asserts the LD_DISC_ bit of the corresponding port.

IACTH is programmable using R23h[0-3].

An internal comparator checks for a proper amplitude

of the oscillator input. If the positive peak of the input

sinusoid falls below a safety value of 2V, OSC_FAIL

sets and the port shuts down. Power cannot be applied

to the ports when ACD_EN is set high and OSC_FAIL is

set high. Leave OSC_IN unconnected or connect it to

DGND when not using AC disconnect detection.

When using the AC disconnect detection feature, con-

nect AGND directly to DNGD as close as possible to

the IC. The MAX5945 also requires a VDD of greater

than +3V for this function. See the Typical Application

Circuit with AC disconnect for other external compo-

nent requirements.

Thermal Shutdown

If the MAX5945 die temperature reaches +150°C, an

overtemperature fault generates and the MAX5945

shuts down and the MOSFETs turn off. The die temper-

ature of the MAX5945 must cool down below +130°C to

remove the overtemperature fault condition. After a

thermal shutdown, the part is reset.

Address Inputs

A3, A2, A1, and A0 represent the four LSBs of the chip

address, the complete 7-bit chip address (see Table 3).

The four LSBs latch on the low-to-high transition of

RESET or after a power-supply start (either on VDD or

VEE). Address inputs default high through an internal

50k

Ω pullup resistor to VDD. The MAX5945 also

responds to the call through a global address 60h (see

the Global Addressing and Alert Response Protocol

section).

I2C-Compatible Serial Interface

The MAX5945 operates as a slave that sends and

receives data through an I2C-compatible, 2-wire or 3-

wire interface. The interface uses a serial data input line

(SDAIN), a serial data output line (SDAOUT), and a ser-

ial clock line (SCL) to achieve bidirectional communica-

tion between master(s) and slave(s). A master (typically

a microcontroller) initiates all data transfers to and from

the MAX5945, and generates the SCL clock that syn-

chronizes the data transfer. In most applications, con-

nect the SDAIN and the SDAOUT lines together to form

the serial data line (SDA).

Using the separate input and output data lines allows

optocoupling with the controller bus when an isolated

supply powers the microcontroller.

The MAX5945 SDAIN line operates as an input. The

MAX5945 SDAOUT operates as an open-drain output.

A pullup resistor, typically 4.7k

Ω, is required on

SDAOUT. The MAX5945 SCL line operates only as an

input. A pullup resistor, typically 4.7k

Ω, is required on

SCL if there are multiple masters, or if the master in a

single-master system has an open-drain SCL output.

Serial Addressing

Each transmission consists of a START condition (Figure

7) sent by a master, followed by the MAX5945 7-bit slave

address plus R/W bit, a register address byte, one or

more data bytes, and finally a STOP condition.

Quad Network Power Controller

for Power-Over-LAN

______________________________________________________________________________________

R/W

Table 3. MAX5945 Address

MAX5945 Datasheet(PDF) 18 Page - Maxim Integrated Products

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