MAX8662ETM+ Maxim Integrated Products, MAX8662ETM+ Datasheet - Page 22

• Manufacturer Part Number: MAX8662ETM+
• Description: IC POWER MANAGE 48-TQFN-EP
• Manufacturer: Maxim Integrated Products

Specifications of MAX8662ETM+

• Applications: Handheld/Mobile Devices
• Current - Supply: 900µA
• Voltage - Supply: 4.1 V ~ 8 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Power-Management ICs for
Single-Cell, Li+ Battery-Operated Devices
The MAX8662/MAX8663 highly integrated PMICs are
designed for use in smart cellular phones, PDAs,
Internet appliances, and other portable devices. They
integrate two synchronous buck regulators, a boost
regulator driving two to seven white LEDs (MAX8662
only), four low dropout (LDO) linear regulators, and a
linear charger for a single-cell Li+ battery. Figure 1 is
the block diagram and application circuit.
SPS circuitry offers flexible power distribution between
an AC adapter or USB source, battery, and system
load, and makes the best use of available power from
the AC adapter/USB input. The battery is charged with
any available power not used by the system load. If a
system load peak exceeds the current limit, supple-
mental current is taken from the battery. Thermal limit-
ing prevents overheating by reducing power drawn
from the input source.
Two step-down DC-DC converters achieve excellent
light-load efficiency and have on-chip soft-start circuit-
ry; 1MHz switching frequency allows for small external
components. Four LDO linear regulators feature low
quiescent current and operate from inputs as low as
1.7V. This allows the LDOs to operate from the step-
down output voltage to improve efficiency. The white
LED driver features easy adjustment of LED brightness
and open-LED overvoltage protection. A 1-cell Li+
charger has programmable charge current up to 1.25A
and a charge timer.
SPS seamlessly distributes power between the external
input, the battery, and the system load (Figure 2). The
basic functions of SPS are:
•
•
•
A thermal-limiting circuit reduces battery-charge rate and
external power-source current to prevent overheating.
22
With both the external power supply and battery
connected:
a) When the system load requirements exceed the
b) When the system load requirements are less than
When the battery is connected and there is no
external power input, the system is powered from
the battery.
When an external power input is connected and
there is no battery, the system is powered from the
external power input.
______________________________________________________________________________________
the capacity of the external power input, the bat-
supplies supplemental current to the load.
capacity of the external power input, the battery
tery is charged with residual power from the input.
Smart Power Selector (SPS)
Detailed Description
All regulated outputs (OUT1–OUT7) derive their power
from the SYS output. With an AC adapter or USB source
connected at DC, the input limiter distributes power
from the external power source to the system load and
battery charger. In addition to the input limiter’s primary
function of passing the DC power source to the system
and charger loads at SYS, it performs several additional
functions to optimize use of available power:
•
•
Figure 2. Smart Power Selector Block Diagram
AC ADAPTER
USB INPUT
Input Voltage Limiting: If the voltage at DC rises,
SYS limits to 5.3V, preventing an overvoltage of the
system load. A DC voltage greater than 6.9V is con-
sidered invalid and the input limiter disconnects the
DC input entirely. The withstand voltage at DC is
guaranteed to be at least 9V. A DC input is also
invalid if it is less than BAT, or less than the DC
undervoltage threshold of 3.5V (falling). With an
invalid DC input voltage, SYS connects to BAT
through a 40mΩ switch.
Input Overcurrent Protection: The current at DC is
limited to prevent input overload. This current limit
is automatically adjusted to match the capabilities
of source, whether it is a 100mA or 500mA USB
source, or an AC adapter. When the load exceeds
the input current limit, SYS drops to 100mV below
BAT and supplemental load current is provided by
the battery.
OR
(DISCHARGE PATH)
DC
BATTERY-TO-SYS
Q1 INPUT-TO-SYS
SWITCH
SWITCH
Q2
MAX8662
MAX8663
(CHARGE
PATH)
Q3
GND
THM
SYS
BAT
Input Limiter
BATTERY
SYSTEM
LOAD
R
THM