NCP370(2008) 查看數據表（PDF） - ON Semiconductor

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NCP370
(Rev.:2008)

Positive and Negative Overvoltage Protection with Internal Low RON N-MOSFETs and Reverse Charge Control Pin

ON Semiconductor 

NCP370

Negative Voltage and Reverse Current.

The device protects the downstream side from negative

voltage occurring on the IN pin, down to −28 V. When a

negative voltage occurs, the output is disconnected from the

IN pins.

Reverse Mode

In Reverse Mode, an external accessory plugged into the

bottom connector can be powered by the internal battery of

the system.

To access to the reverse mode, DIR pin must be tied high

(> 1.2) and REV must be tied high to low (< 0.55 V).

In this case, the core of the NCP370 will be supplied by the

battery, with a 2.5 V minimum voltage and 5.5 V maximum

voltage.

In this reverse state, both OCP and thermal modes are

available.

Overcurrent Protection (OCP)

This device integrates the reverse over current protection

function, from battery to external accessory.

That means the current across the internal NMOS is

limited when the value, set by the external Rlimit resistor,

exceeds IOCP.

An internal resistor is placed in series with the Ilim pin

allowing a maximum OCP value when Ilim pin is directly

connected to GND.

By adding external resistors in series from Ilim to GND,

the OCP value is lowered. See below table:

Typical Current clamp table:

Table 3. OVERCURRENT THRESHOLD SELECTION

OCP

(A)

RLIMIT

(kW)

1.6

0

1.0

14

0.5

70

During an overcurrent event, the N−MOSFETs turn off

and FLAG output goes low, allowing the micro−controller

to process the fault event and then disable reverse charge

path.

At power up (accessory is plugged on input pins), the

current is limited up to Ilim for 1.2 ms (typical), to allow

capacitor charge and limit inrush current. If the Ilim

threshold is exceeded over 1.2 ms, the device enters

OCP burst mode until the overcurrent event disappears.

After 1 ms following the plug in of the accessory, the OCP

mode is engaged. See Figure 5.

Vout

Vin

FLAG

tonREV

tstartREV

tREG

IREV

REV

ID

tRRD

Drive Current in Accessory

Ilim

Accessory ID

Detection

DIR

Figure 5. Overcurrent Protection Sequence

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