MAX1586A Datasheet, PDF (20/32 Pages) Maxim Integrated Products – High-Efficiency, Low-IQ PMICs with Dynamic Core for PDAs and Smart Phones

High-Efficiency, Low-I_Q PMICs with
Dynamic Core for PDAs and Smart Phones
out of regulation, V7 is sourced from BKBT by a second
on-chip MOSFET. V7 can supply loads up to 30mA. V7
is intended to connect to VCC_BATT on Intel CPUs.
Due to variations in system implementation, BKBT and
V7 can be utilized in different ways. See the Backup-
Battery Configurations section for information on how to
use BKBT and V7.
Quiescent Operating Current
in Various States
The MAX1586/MAX1587 are designed for optimum effi-
ciency and minimum operating current for all typical
operating modes, including sleep and deep sleep.
These states are outlined in Table 1.
Voltage Monitors, Reset, and
Undervoltage-Lockout Functions
Undervoltage Lockout
When the input voltage is below 2.35V (typ), an under-
voltage-lockout (UVLO) circuit disables the IC. The
inputs remain high impedance while in UVLO, reducing
battery load under this condition. All serial registers are
maintained with the input voltage down to at least 2.35V.
Reset Output (RSO) and MR Input
The reset output (RSO) is low when the MR input is low
or when V7 is below 2.425V. V7 is powered from V1
(when enabled) or the backup-battery input (BKBT).
RSO normally goes low:
1) When power is first applied in configurations with
no separate backup battery (external diode from
IN to BKBT).
2) When power is removed in configurations with no
separate backup battery (external diode from IN
to BKBT).
3) If the backup battery falls below 2.425V when V1
is off or out of regulation.
4) When the manual reset button is pressed (MR
goes low).
RSO has a timer that delays release until 65ms after V7
exceeds 2.3V when V_IN > 2.4V. If V_IN < 2.4V when V7
exceeds 2.3V, RSO deasserts immediately with no 65ms
delay. There is no delay in this case because the timer
circuitry is deactivated to minimize operating current dur-
ing IN undervoltage lockout. RSO is not triggered by any
output besides V7. If BKBT is not powered, RSO does
not function and is high impedance.
MR is a manual reset input for hardware reset. When MR
goes low, RSO asserts for a minimum of 65ms. MR does
not reset any internal MAX1586/MAX1587 functions.
MAIN BATTERY
R1
438kΩ
R2
62kΩ
R3
200kΩ
IN
MAX1586
DBI (1.232V THRESHOLD)
LBI (1.00V THRESHOLD)
Figure 2. Setting the Low-Battery and Dead-Battery Thresholds
with One Resistor Chain. The values shown set a DBI threshold
of 3.3V and an LBI threshold of 3.5V (no resistors are needed
for the factory preset thresholds).
Dead-Battery and Low-Battery Comparators—
DBI, LBI (MAX1586 only)
The DBI and LBI inputs monitor input power (usually a
battery) and trigger the DBO and LBO outputs. The
dead-battery comparator triggers DBO when the battery
(V_IN) discharges to the dead-battery threshold. The
factory-set 3.15V threshold is selected by connecting
DBI to IN, or the threshold can be programmed with a
resistor-divider at DBI. The low-battery comparator has
a factory-set 3.6V threshold that is selected by connect-
ing LBI to IN, or its threshold can be programmed with a
resistor-divider at LBI.
One three-resistor-divider can set both DBI and LBI
(R1, R2, and R3 in Figure 2) according to the following
equations:
1) Choose R3 to be less than 250kΩ
2) R1 = R3 V_LB (1 - (1.232 / V_DB))
3) R2 = R3 (1.232 x (V_LB / V_DB) - 1)
where V_LB is the low-battery threshold and V_DB is the
dead-battery threshold.
Alternately, LBI and DBI can be set with separate two-
resistor-dividers. Choose the lower resistor of the divider
chain to be 250kΩ or less (R5 and R7 in Figure 3). The
equations for upper divider-resistors as a function of
each threshold are then:
R4 = R5 (V_DB / 1.232) - 1)
R6 = R7 (V_LB - 1)
When resistors are used to set V_LB, the threshold at LBI
is 1.00V. When resistors are used to set V_DB, the
threshold at DBI is 1.232V. A resistor-set threshold can
20 ______________________________________________________________________________________