NCV890430

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8

RESET Function

The RSTB pin is pulled low when the output voltage falls

below 8% of the nominal regulation level, and floats when

the output is properly regulated. A pull-up resistor tied to the

output is needed to generate a logic high signal on this

open-drain pin. The pin can be left unconnected when not

used.

When the output voltage drops out of regulation, the pin

stays low for a delay time (adjustable) after the output goes

back

to

regulation,

simplifying

the

connection

to

a micro-controller.

The RSTB signal can either be used as a reset with delay

or a power good (no delay). The delay is determined by the

current into the RSTB pin, set by a resistor, as shown in

Figure 7.

Use the following equation to determine the ideal reset

delay time using currents less than 500

mA:

t

2500

I

RSTB

(eq. 1)

mA]

reset to act as a “power good” pin.

Figure 7. Reset with Adjustable Delay

on a Single Pin

VOUT

RST

RSTB

The RSTB resistor is commonly tied to VOUT.

Depending on the output voltage option, typical delay times

can be achieved with the following resistor values:

Table 4. TYPICAL DELAY TIMES

5

−

−

5

10

5

7.6

10

20

10

15

20

30

15

23

−

50

25

−

−

Enable

The NCV890430 is designed to accept either a logic-level

signal or battery voltage as an Enable signal. However, if

voltages above 40 V are expected, EN should be tied to VIN

through a 10 k

W resistor in order to limit the current flowing

into the overvoltage protection of the pin.

A low signal on Enable induces a shutdown mode which

shuts off the regulator and minimizes its supply current to

less than 5

mA by disabling all functions.

Once the switching regulator output is enabled, a soft-start

is always initiated.

Thermal Shutdown

A thermal shutdown circuit inhibits switching and resets

the soft-start circuit if internal temperature exceeds a safe

level. Switching is automatically restored when temperature

returns to a safe level.

Exposed Pad

The exposed pad (EPAD) on the back of the package must

be electrically connected to both the analog and the power

electrical ground GND and PGND pins for proper,

noise-free operation. It is recommended to connect these 2

pins directly to the EPAD with a PCB trace.

DEVICE ORDERING INFORMATION

Device

Output

Marking

Package

NCV890430MW50TXG

5.0 V

TBD

DFN8

(Pb−Free)

TBD / Tape & Reel

NCV890430MW33TXG

3.3 V

TBD

NCV890430MW25TXG

2.5 V

TBD

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.