It's all about power nowadays
as consumers snap up
portable devices that require
more and more juice. Designers are hard pressed to keep
users' tanks topped up and to
give those users an idea of
how far they can go on what's
left in those tanks. Maxim's
latest solutions include a pair
of power-management ICs as
well as a programmable fuel
gauge that can be built into
battery packs.
The MAX8662 and MAX8663 do more than integrate two synchronous buck regulators, a boost regulator driving two to seven white LEDs, four low-dropout linear
regulators (LDOs), and a linear charge for a single-cell lithium-ion (Li+)
battery (). When system load peaks
exceed the external source's capability,
both ICs tell the battery to supply whatever supplemental current is needed.
When system load requirements are
low, residual power from the external
power source will be directed to charging
the battery. When external power is connected, the system can operate with no
battery or a discharged battery. The
external power source can be an ac
adapter, an auto adapter, or a USB source. The ICs are intended for smart cellular phones, PDAs, Internet appliances, and other portable devices.
The MAX8663 integrates two
high-efficiency step-down dc-dc
converters, four LDOs, and the
smart charger. The MAX8662
adds the step-up dc-dc converter for up to seven white or
organic LED or displays. Specs
for both buck converters
include up to 97% efficiency at
1- to 3.3-V output. One handles 1.2-A loads, the other 900-mA
loads. The four LDOs support
500-, 300-, and two 150-mA loads. Input range is from 1.7 to 5.5 V.
The LDOs also have selectable output
voltages to eliminate external resistor-dividers and minimize board space.
The charger's dc-input current limit is
adjustable up to 2 A. Charge current is
adjustable up to 1.5 A to accommodate
a wide range of battery capacities. The
chips provide thermal regulation, overvoltage protection, charge status and
fault outputs, a power-OK monitor, a battery-thermistor monitor, and a charge timer. Pricing starts at $3.95.
ROLL YOUR OWN CODE
The DS2792 from Maxim's
Dallas Semiconductor division
offers a programmable fuel
gauge that can be built into
one- or two-cell battery packs.
Battery-pack designers who
aren't satisfied with pre-programmed fuel-gauging algorithms can use the chip to
write their own code or tweak
existing code.
The chip integrates a microcontroller, password-protected
program memory, data memory, and an accurate measurement system for battery current, voltage, and temperature
(). Its computing core is
the low-power, 16-bit MAXQ20 microcontroller. Fetch and execution operations
are completed in one cycle without
pipelining.
A 16-level hardware stack enables
fast subroutine calls and task-switching.
The DS2792 contains separate program
memory, data EEPROM, and data RAM.
I/O is via JTAG or a 19.2-kbit/s UART
interface. Programming can take place
through either port.
Current measurements are internally
summed to calculate the accumulated current. That measurement is accurate to within 0.5%, ±4.0 µV, over a range of
±64 mV. Based on the use of a
15-mΩ sense resistor, this
translates to 0.5%, ±267 µA,
over a 4.2-A range.
The DS2792 measures voltage as a 10-bit value over a 0- to 4.99-V range with a resolution
of 4.88 mV. Its temperature
sensor measures the temperature of the battery and reports
the results as a 10-bit value
with a resolution of 0.125°C.
Pricing starts at $3.28.
Maxim Integrated Products
www.maximic.com