Rainbow-electronics MAX8620 Manual de usuario descargar pdf (Pagina 11)

Hands-Free Enable Input (HF_PWR)

A rising edge at HF_PWR generates an internal one-

shot pulse that enables the MAX8620Y for 1.31s (t

). If

HF_PWR remains high after t

expires, the MAX8620Y

reenters shutdown. During t

OUT3 and OUT1 are

enabled so the microprocessor (µP) can initialize and

assert a logic-high at PWR_ON. OUT2 enables during

if EN2 is low. Once PWR_ON is high, the status of

HF_PWR is ignored. If PWR_ON remains low after t

expires, the MAX8620Y reenters shutdown.

Power-Supply Sequencing

The step-down converter output (OUT3) always powers

up first and powers down last (Figure 4). OUT1 powers

approximately 70µs after OUT3, and OUT2 powers

approximately 50µs after V

OUT1

reaches 87% (typ) of

its regulation voltage. When PWR_ON goes low, OUT1

turns off, then OUT2 turns off, then OUT3 turns off 50µs

after PWR_ON goes low.

MAX8620Y

µPMIC for Microprocessors or DSPs

in Portable Equipment

______________________________________________________________________________________ 11

HF_PWR

PWR_ON

OUT3

OUT1

SU2

THR

SU1

OUT2

RESET

EN2

50µs

Figure 4. MAX8620Y Power-Supply Sequencing

Table 2. MAX8620Y Power Modes

PWR_ON HF_PWR* EN2 OUT1 AND OUT3 OUT2

1 X 1 Enabled Disabled

1 X 0 Enabled Enabled

0 1 1 Enabled Disabled

0 1 0 Enabled Enabled

0 0 X Disabled Disabled

*A rising edge at HF_PWR initiates a 1.31s one-shot timer. The status of HF_PWR shown in Table 2 indicates whether the one-shot

period has expired as follows:

1 = During t

0 = t

has expired

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 17 18

MAX8620Y 1

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Rainbow-electronics MAX8620 Manual de usuario Pagina 11

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