MCP16501 datasheet(21/42 Pages) MICROCHIP

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DS20006388E-page 21

MCP16501

For the different OTP options for the t1 to t4 timings, see

the respective values in “Configuration Options”.

For power supplies starting at t1, additional delay time

interval is added to the device wake-up time.

The following timing diagram in Figure 4-5 shows the

typical sequence for Case 2:

FIGURE 4-5:

Start-Up from PWRHLD

Timing Diagram.

For all sequences described above, LPM can be

assumed to be low. The MPU will assert LPM after

some time, based on software decision, to enter the

Low-Power mode.

4.4.2

POWER-UP SEQUENCE

FLOWCHART

The start-up sequence is divided into three steps and

each Buck regulator is assigned to a specific sequence

step:

• Step 1 (Buck1) regulator is started after a delay

(t1) from the start-up event. If the start-up event is

no longer valid as the instant t1 expires, the

start-up sequence is aborted before the first regu-

lator is started.

• Step 2 (Buck2) regulator is started after a delay

(t2) since the completion of the sequence Step 1

(regulator enabled at Step 1 has been powered up

correctly).

• Step 3 (Buck3) regulator is started after a delay

(t3) from the completion of the sequence Step 2

(regulator enabled at Step 2 has been powered up

correctly).

The subsequent assertion of nRSTO is determined by

the status of all regulators that have been turned on

during the power-up sequence Their status is checked

before starting counter t4 and again checked at the

expiration of t4 to have nRSTO deasserted.

After the completion of the power-up sequence (i.e., at

the time instant nRSTO is deasserted), the MCP16501

will enter the Power modes state machine operation

defined by the LPM and PWRHLD signals, and the cor-

responding device setting.

Some regulators which are supposed to turn on in the

power-up sequence may fail to power-up correctly.

In this case, the sequencing engine adds a 32 ms

waiting time to allow the affected regulators to recover.

After the expiration of the 32 ms period, if the affected

regulators have still not recovered, the start-up

sequence is aborted and the MCP16501 returns to its

OFF state.

The start-up sequence flowchart is described in

Figure 4-6.

Where:

t1 = Delay from PWRHLD asserted to first

output VOUT1 starting (default 0.5 ms +

device wake-up time, about 100 µs)

t2 = Time from VOUT1 established to VOUT2

starting (default 8 ms)

t3 = Time from VOUT2 established to VOUT3

starting (default 4 ms)

t4 = Time from VOUT3 established to nRSTO

deassertion (default 16 ms)

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