ISL8201MEVAL1Z datasheet(8/16 Pages) RENESAS

8 / 16 page

ISL8201M

FN6657 Rev 3.00

Page 8 of 16

October 28, 2014

Applications Information

The typical ISL8201M application schematic for input voltage

+5V or +12V is shown in Figure 11. External component

selection is primarily determined by the maximum load current

and input/output voltage.

Programming the Output Voltage

The ISL8201M has an internal 0.6V ±1.5% reference voltage.

Programming the output voltage requires a dividing resistor

(RFB). The output voltage can be calculated as shown in

Equation 1:

Note: ISL8201M has integrated 9.76k

 resistance into the

module (dividing resistor for top side). The resistance

corresponding to different output voltages is as shown in

Table 1:

Initialization (POR and OCP Sampling)

Figure 13 shows a start-up waveform of ISL8201M. The

power-on-reset (POR) function continually monitors the bias

voltage at the PVCC pin. Once the rising POR threshold has

exceeded 4V (VPORR nominal), the POR function initiates the

overcurrent protection (OCP) sample and hold operation (while

COMP/EN is ~1V). When the sampling is complete, VOUT

begins the soft-start ramp.

If the COMP/EN pin is held low during power-up, the

initialization will be delayed until the COMP/EN is released and

its voltage rises above the VENDIS trip point.

Figures 14 and 15 show a typical power-up sequence in more

detail. The initialization starts at t0, when either PVCC rises

above VPORR, or the COMP/EN pin is released (after POR).

The COMP/EN will be pulled up by an internal 20µA current

source, however, the timing will not begin until the COMP/EN

exceeds the VENDIS trip point (at t1). The external capacitance

of the disabling device, as well as the compensation

capacitors, will determine how quickly the 20µA current source

will charge the COMP/EN pin. With typical values, it should

add a small delay compared to the soft-start times. The

COMP/EN will continue to ramp to ~1V.

From t1, there is a nominal 6.8ms delay, which allows the

PVCC pin to exceed 6.5V (if rising up towards 12V), so that the

internal bias regulator can turn on cleanly. At the same time,

the ISET pin is initialized by disabling the low-side gate driver

and drawing ISET (nominal 21.5µA) through RSETI. This sets up

a voltage that will represent the ISET trip point. At t2, there is a

variable time period for the OCP sample and hold operation

(0.0ms to 3.4ms nominal; the longer time occurs with the

higher overcurrent setting). The sample and hold uses a digital

counter and DAC to save the voltage, so the stored value does

not degrade, as long as the PVCC is above VPORR (See

“Overcurrent Protection (OCP)” on page 10 for more details on

the equations and variables). Upon the completion of sample

and hold at t3, the soft-start operation is initiated, and the

output voltage ramps up between t4 and t5.

TABLE 1. RESISTANCE TO OUTPUT VOLTAGES

VOUT

0.6V

1.05V

1.2V

1.5V

RFB

open

13k

9.76k

6.49k

VOUT

1.8V

2.5V

3.3V

RFB

4.87k

3.09k

2.16k

1.33k

VOUT

0.6

9.76k

RFB

---------------







(EQ. 1)

FIGURE 13. POR AND SOFT-START OPERATION

PVCC

VOUT

COMP/EN

~4V

FIGURE 14. ISET AND SOFT-START OPERATION

COMP/EN

ISET

VOUT

ISET

VOUT

COMP/EN

ISL8201MEVAL1Z Datasheet(PDF) 8 Page - Renesas Technology Corp

ISL8201MEVAL1Z Datasheet(HTML) 8 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Datasheet Download

Link URL