Rainbow Electronics MAX8620 - Manual (Page 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
HF ). If
HF_PWR remains high after t HF expires, the MAX8620Y
reenters shutdown. During t HF
, OUT3 and OUT1 are
enabled so the microprocessor (µP) can initialize and
assert a logic-high at PWR_ON. OUT2 enables during
t
HF
if EN2 is low. Once PWR_ON is high, the status of
HF_PWR is ignored. If PWR_ON remains low after t HF
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
t SU2
V THR
t SU1
t RP
t HF
OUT2
RESET
EN2
50 µs
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 HP
0 = t HP has expired