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ACT8740 Schematic ( PDF Datasheet ) - Active-Semi

Teilenummer ACT8740
Beschreibung Six Channel Integrated Power Management IC
Hersteller Active-Semi
Logo Active-Semi Logo 




Gesamt 40 Seiten
ACT8740 Datasheet, Funktion
ACT8740
Rev PrB, 25-Feb-08
Advanced Product InformationAll Information Subject to Change
Six Channel Integrated Power Management IC
for Handheld Portable Equipment
FEATURES
Multiple Patents Pending
Li+ Battery Charger with Integrated MOSFET
Programmable Charge Current up to 1A
ON/OFF Control
Five Integrated Regulators
350mA PWM Step-Down DC/DC
Step-Up DC/DC with OVP for WLED Bias
350mA Low Noise LDO
250mA Low Noise LDO
250mA Low Noise LDO
I2CTM Compatible Serial Interface
Programmable Output Voltages
Configurable Operating Modes
Minimal External Components
4x4mm, Thin-QFN (TQFN44-24) Package
Only 0.75mm Height
RoHS Compliant
APPLICATIONS
Portable Devices and PDAs
Wireless Handhelds
DMB Enabled Devices
GPS Receivers, etc.
GENERAL DESCRIPTION
The patent-pending ACT8740 is a complete, cost
effective, highly-efficient ActivePMUTM power man-
agement solution that is ideal for a wide range of
portable handheld equipment. This device integrates
one PWM step-down DC/DC converter, one PWM
step-up DC/DC converter with over-voltage protec-
tion (OVP), three low dropout linear regulators
(LDOs) and a full-featured linear-mode Li+ battery
charger into a single, thin, space-saving package.
An I2C Serial Interface provides programmability for
the DC/DC converters, LDOs and battery charger.
REG1 is a fixed-frequency, current-mode PWM step
-down DC/DC converter that is optimized for high
efficiency and is capable of supplying up to 350mA
output current. REG2 is a fixed-frequency, step-up
DC/DC converter that safely and efficiently biases a
string of up to seven white-LEDs for backlighting.
REG3, REG4, and REG5 are low noise, high PSRR
linear regulators that are capable of supplying up to
350mA, 250mA, and 250mA, respectively. The bat-
tery charger incorporates an internal power MOS-
FET for constant-current/constant-voltage, thermally
regulated charging of a single-cell Li+ battery. All
DC/DC converters and LDOs output voltages are
programmable and controllable via the I2C interface.
The ACT8740 is available in a tiny 4mm x 4mm
24-pin Thin-QFN package that is just 0.75mm thin.
SYSTEM BLOCK DIAGRAM
VIN
CHGLEV
Single-Cell Li+
Battery Charger
nMSTR
nIRQ
SCL
SDA
ON1
System Control
ACT8740
PMUActive
TM
REG1
Step-Down
DC/DC
REG2
Step-Up
DC/DC
REG3
LDO
REG4
LDO
REG5
LDO
Innovative Products. Active Solutions.
ActivePMUTM is a trademark of Active-Semi.
I2CTM is a trademark of Philips Electronics.
-1-
Battery
Programmable
Up to 1A
OUT1
1.1V to 4.4V
Up to 350mA
OUT2
WLED Bias
OUT3
1.4 to 3.7V
Up to 350mA
OUT4
1.4 to 3.7V
Up to 250mA
OUT5
1.4 to 3.7V
Up to 250mA
Pb-free
www.active-semi.com
Copyright © 2008 Active-Semi, Inc.
Free Datasheet http://www.datasheet4u.com/






ACT8740 Datasheet, Funktion
ACT8740
Rev PrB, 25-Feb-08
PIN DESCRIPTIONS CONT’D
PIN NAME
DESCRIPTION
18
REFBP
Reference Noise Bypass. Connect a 0.01µF ceramic capacitor from REFBP to GA. This pin is
discharged to GA in shutdown.
19
FB2
Feedback Sense for REG2. Connect this pin to the LED string current sense resistor to sense
the LED current.
20
OVP2
Over-Voltage Protection Input for REG2. Connect this pin directly to the output node to sense
and prevent over-voltage conditions.
21
GP2
Power Ground for REG2. Connect GP2 directly to a power ground plane. Connect GA, GP1
and GP2 together at a single point as close to the IC as possible.
22 SW2 Switching Node Output for REG2. Connect this pin to the switching end of the inductor.
Tri-State Charging State Select Input. When ISET1[ ] = [0000], drive CHGLEV to VSYS or to a
23 CHGLEV logic high for high-current charging mode (450mA), and drive to GA or a logic low for low-
current charging mode (90mA). Allow CHGLEV to float (|ICHGLEV| < 2µA) to disable the charger.
24
BAT
Output Voltage for the Battery Charger. Connect this pin directly to the battery anode (+ termi-
nal) to sense the battery voltage.
EP EP Exposed Pad. Must be soldered to ground on PCB.
Innovative Products. Active Solutions.
ActivePMUTM is a trademark of Active-Semi.
I2CTM is a trademark of Philips Electronics.
-6-
www.active-semi.com
Copyright © 2008 Active-Semi, Inc.
Free Datasheet http://www.datasheet4u.com/

6 Page









ACT8740 pdf, datenblatt
ACT8740
Rev PrB, 25-Feb-08
SYSTEM MANAGEMENT
FUNTIONAL DESCRIPTION
General Description
The ACT8740 offers an array of system manage-
ment functions that allow it to provide optimal per-
formance in a wide range of applications.
I2C Serial Interface
At the core of the ACT8740’s flexible architecture is
an I2C interface that permits optional programming
capability to enhance overall system performance.
To ensure compatibility with a wide range of system
processors, the ACT8740 uses standard I2C com-
mands, I2C write-byte commands are used to pro-
gram the ACT8740 and I2C read-byte commands
are used to read the ACT8740’s internal registers.
The ACT8740 always operates as a slave device,
and is addressed using a 7-bit slave address fol-
lowed by an eighth bit, which indicates whether the
transaction is a read-operation or a write-operation,
[1011110x].
SDA is a bi-directional data line and SCL is a clock
input. The master initiates a transaction by issuing a
START condition, defined by SDA transitioning from
high to low while SCL is high. Data is transferred in
8-bit packets, beginning with the MSB, and is
clocked-in on the rising edge of SCL. Each packet
of data is followed by an “Acknowledge” (ACK) bit,
used to confirm that the data was transmitted suc-
cessfully.
For more information regarding the I2C 2-wire serial
interface, go to the NXP website: http://www.nxp.com
System Startup and Shutdown
The ACT8740 features a flexible control architec-
ture that supports a variety of software-controlled
enable/disable functions that make it a simple yet
flexible and highly configurable solution.
The ACT8740 is automatically enabled when any of
the following conditions exists:
1) A valid supply voltage is present at VIN,
2) nMSTR is asserted low, or
3) ON1 is asserted high.
If any of these conditions is true, the ACT8740 en-
ables REG1 and REG3, powering up the system
processor so that the startup and shutdown se-
quences may be controlled via software. Each of
these startup conditions are described in detail below.
Automatic Enable Due to Valid VIN Supply
The ACT8740 battery charger, REG1, and REG3
are automatically enabled when a valid input supply
is applied to VIN. Automatically enabling these
functions simplifies system design and eliminates
the need for external input supply-detection cir-
cuitry.
Manual Enable Due to Asserting nMSTR Low
System startup is initiated when the user presses
the push-button, asserting nMSTR low. When this
occurs, both REG1 and REG3 are enabled. Once
the power-up routine is successfully completed, the
microprocessor must assert ON1 so that the
ACT8740 remains enabled after the push-button is
released by the user. Upon completion of the start-
up sequence the processor assumes control of the
power system and all further operation is software-
controlled.
Manual Enable Due to Asserting ON1 High
The ACT8740 is compatible with applications that
do not utilize its push-button control function, and
may be enabled by simply driving ON1 to a logic-
high. In this case, the signal driving ON1 controls
enable/disable timing, although software-controlled
enable/disable sequences are still supported if the
processor assumes control of the power system
once the startup sequence is completed.
Shutdown Sequence
Once a successful power-up routine is completed,
the system processor controls the operation of the
power system, including the system shutdown tim-
ing and sequence. The ACT8740 asserts nIRQ low
when nMSTR is asserted low, providing a simple
means of alerting the system processor when the
user wishes to shut the system down. Asserting
nIRQ interrupts the system processor, initiating an
interrupt service routine in the processor which will
reveal that the user pressed the push-button. The
microprocessor may validate the input, such as by
ensuring that the push-button is asserted for a mini-
mum amount of time, then initiates a software-
controlled power-down routine, the final step of
which is to de-assert the ON1 input, disabling
REG1 and REG3 and shutting the system down.
Innovative Products. Active Solutions.
ActivePMUTM is a trademark of Active-Semi.
I2CTM is a trademark of Philips Electronics.
- 12 -
www.active-semi.com
Copyright © 2008 Active-Semi, Inc.
Free Datasheet http://www.datasheet4u.com/

12 Page





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