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PDF ACT8700 Data sheet ( Hoja de datos )
| Número de pieza | ACT8700 | |
| Descripción | Four Channel Integrated Power Management IC | |
| Fabricantes | Active-Semi | |
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ACT8700
Rev PrA 08/2006
Advanced Product Information—All Information Subject to Change
FOUR CHANNEL INTEGRATED POWER MANAGEMENT IC
FOR HANDHELD PORTABLE EQUIPMENT
FEATURES
• Four Integrated Regulators
350mA PWM Step-Down DC/DC
500mA PWM Step-Down DC/DC
Step-Up DC/DC for WLED Bias
Complete Li+ Battery Charger
• Minimal External Components
• 4x4mm, Thin-QFN44-24 (TQFN) Package
APPLICATIONS
• Portable Media Players
• Digital Camera Modules
• GPS Receivers
• PDAs
ACT8700 contains circuitry with multiple patents pending.
GENERAL DESCRIPTION
The ACT8700 is a complete, cost-effective
ActivePMU™ power management solution with
multiple patents pending for portable handheld
equipment. This device integrates all four regulators
required for small portable devices — two step-down
DC/DCs for processor core and I/O power, a step-up
DC/DC for WLED bias, and a complete, stand-alone
Li+ battery charger — into a single, space-saving
package.
REG1 and REG2 are fixed-frequency, current-mode
PWM step-down DC/DC converters that are capable
of supplying up to 350mA and 500mA, respectively.
REG1 and REG2 are available with a variety of
factory-preset output voltage combinations. REG3 is
a fixed-frequency, step-up DC/DC converter that
provides efficient display backlight bias to a string of
up to six white-LEDs. Finally, the ACT8700 also
contains a complete, thermally-regulated, stand-
alone single-cell Li+ charger.
The ACT8700 is available in a tiny 4mm x 4mm 24-
pin Thin-QFN package that is just 0.75mm thick.
SYSTEM BLOCK DIAGRAM
Innovative Products. Active Solutions.
-1-
Active Semi Confidential—Do Not Copy or Distribute
www.active-semi.com
Copyright ® 2006, Active-Semi Inc.
Free Datasheet http://www.datasheet4u.com/
1 page  
Advanced Product Information.
All Information Subject to Change
FUNCTIONAL BLOCK DIAGRAM
ACT8700
Innovative Products. Active Solutions.
-5-
Active Semi Confidential—Do Not Copy or Distribute
www.active-semi.com
Copyright ® 2006, Active-Semi Inc.
Free Datasheet http://www.datasheet4u.com/
5 Page 
Advanced Product Information.
All Information Subject to Change
ACT8700
STEP-DOWN DC/DC CONVERTERS (REG1 AND REG2)
FUNCTIONAL DESCRIPTION
General Description
REG1 and REG2 are fixed-frequency current-mode
synchronous PWM step down converters that
achieve peak efficiency of over 95%. REG1 is capa-
ble of supplying up to 350mA of output current, while
REG2 supports up to 500mA. Under light load condi-
tions, these regulators utilize a proprietary pulse
skipping control scheme that consumes just 24µA of
supply current, maximizing battery life and making
them ideal for portable applications. These regulators
operate with a fixed frequency of 1.7MHz, minimizing
noise in sensitive applications and allowing the use
of small external components.
REG1 and REG2 operate out of phase to minimize
both the size and cost of the required input capacitor.
The ACT8700 is available with a variety of standard
REG1 and REG2 output voltages. Contact the fac-
tory for other available voltage options or to inquire
about custom output voltage requirements.
100% Duty Cycle Operation
Although REG1 and REG2 have been optimized to
maximize efficiency in lower output voltage applica-
tions, both regulators are capable of operating at up
to 100% duty cycle to ensure the lowest possible
dropout voltage.
Synchronous Rectification
In order to maximize efficiency and minimize the total
solution size and cost, REG1 and REG2 both feature
integrated synchronous rectifiers that eliminate the
need for an external rectifier.
REG1 and REG2 feature adaptive reverse current
limit circuitry that engages during PWM operation to
maintain regulation with a constant switching fre-
quency without the need for a minimum load.
Operating Modes
In order to maximize efficiency over the full load cur-
rent range, REG1 and REG2 operate with fixed-
frequency PWM operation under medium to high
load conditions, and utilize a proprietary and patent-
pending control scheme at light loads to reduce qui-
escent supply current to just 24µA to ensure the
highest possible light-load efficiency. This combina-
tion of control schemes maximizes efficiency over
the full load current range while avoiding the high
output voltage ripple caused by “pulse-grouping” be-
havior of competing light-load control schemes.
Enabling and Disabling REG1 and REG2
REG1 and REG2 are automatically enabled when-
ever 1) an input supply is present on VIN, 2) nMSTR
is driven low, or 3) ON1 is driven high. When dis-
abled, each regulator's quiescent supply current
drops to just 1µA.
Enable/disable functionality is typically implemented
as part of a controlled enable/disable scheme utiliz-
ing nMSTR and other features of the ACT8700 sys-
tem controller. See the System Startup & Shutdown
section for more information.
Innovative Products. Active Solutions.
- 11 -
Active Semi Confidential—Do Not Copy or Distribute
www.active-semi.com
Copyright ® 2006, Active-Semi Inc.
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet ACT8700.PDF ] | |
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