NCV7702B

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7

Functional Description

The NCV7702B is arranged as four half-bridge drivers in

two independent channels. Each channel can be operated as

a full-bridge or half-bridge to drive multiple load

configurations. Separate ENable inputs are used to control

which channel is active. Each ENable input has a nominal

50 k

W internal pull-down resistor to ensure that the outputs

address each half-bridge output, and each output follows the

Half-Bridge Drivers

an NPN Darlington driver on the low-side and a compound

PNP-NPN driver on the high-side. Each half-bridge driver

is capable of 1 A (min) peak current and is overcurrent

protected against load and system faults. Cross conduction

currents within each half-bridge are suppressed by the use

input contains an

independent dead-band timer that is activated on either

edge of the input transition.

Overcurrent detection circuitry is provided in both the

low-side and high-side drivers of each half-bridge output.

When activated, the overcurrent detectors trigger an internal

timer which causes both half-bridge drivers in the same

channel to be modulated at 4% (Typ.) duty cycle. The timer

also activates the channel's STATUS output, causing it to be

similarly modulated (see Figure 5.) Upon removal of the

fault condition, the channel automatically resumes

operation in its previously programmed mode and its

STATUS output returns to a no-fault state.

to either VB or PGND and help contain switching currents

within each load loop.

Overcurrent Duty Cycle Timer

A single timer for overcurrent duty cycle is common to

both channels. The timer is triggered when a half-bridge in

either channel has detected an overcurrent fault. An external

program the period of the timer, and the ratio of two

internally fixed currents programs the timer's duty cycle.

The capacitor voltage is normally kept at zero by discharge

charging from zero towards the timer's upper threshold

channel's outputs are switched off and the channel's

The charging current is switched off, and the capacitor

Upon crossing the lower threshold, the channel's outputs are

switched on and the channel's STATUS output returns to its

condition is resolved. If the fault condition is resolved

of the previously faulted channel's half-bridge or STATUS

outputs occurs.

After the timer's initial charge cycle, the output off time

is:

The output on time is:

The timer period is:

of 470 to 1500 pF. Values below 470 pF may cause timer

mis-operation due to internal delays, while values above

1500

pF

may

cause

excessive

power

dissipation.

the current limit function.

Overvoltage and Overtemperature Protection

Overvoltage detection circuitry is intended to allow

limited operation of the NCV7702B during double-battery

conditions. Detection is via the VB1 pin and causes both

channels of the IC to be switched off when the detection

threshold is exceeded. Hysteresis is provided to improve

noise immunity of the overvoltage function.

Overtemperature

detection

circuitry

monitors

the

junction temperature internal to the IC and is intended to

ensure

reliability

by

preventing

excessive

power

dissipation. The detection circuitry is centrally located on

the IC and causes both channels of the IC to be switched off

when the detection threshold is exceeded. Hysteresis is

provided to improve noise immunity of the overtemperature

function.

during either overvoltage or overtemperature faults. Normal

operation of the IC is resumed automatically upon resolution