CDH2D09 View Datasheet(PDF) - Maxim Integrated
Part Name
Description
MFG CO.
'CDH2D09' PDF : 44 Pages View PDF
PMIC with Integrated Charger and
Smart Power Selector for Handheld Devices
with a single power input to operate from either an AC-
to-DC adapter or USB host (see Table 1).
A thermal-limiting circuit reduces the battery charger
rate and external power-source current to prevent the
MAX8671X from overheating.
System Load Switch
An internal 80mΩ (RBS) MOSFET connects SYS to BAT
when no voltage source is available at DC or USB.
When an external source is detected at DC or USB, this
switch is opened and SYS is powered from the valid
input source through the Smart Power Selector.
When the system load requirements exceed the input
current limit, the battery supplies supplemental current
to the load through the internal system load switch. If
the system load continuously exceeds the input current
limit, the battery does not charge, even though external
power is connected. This is not expected to occur in
most cases because high loads usually occur only in
short peaks. During these peaks, battery energy is
used, but at all other times the battery charges.
USB Power Input (USB)
USB is a current-limited power input that supplies the
system (SYS) up to 500mA. The USB to SYS switch is a
linear regulator designed to operate in dropout. This lin-
ear regulator prevents the SYS voltage from exceeding
5.3V. USB is typically connected to the VBUS line of the
universal serial bus (USB) interface. As shown in Table
1, USB supports three different current limits that are
set with the PEN2 and USUS digital inputs. These cur-
rent limits are ideally suited for use with USB power.
The operating voltage range for USB is 4.1V to 6.6V,
but it can tolerate up to 14V without damage. When the
USB input voltage is below the undervoltage threshold
(VUSBL, 4V typ) it is considered invalid. Similarly, if the
USB voltage is above the overvoltage threshold
(VUSBH, 6.9V typ) it is considered invalid. When the
USB voltage is below the battery voltage, it is consid-
ered invalid. The USB power input is disconnected
when the USB voltage is invalid. As shown in Table 1,
when power is available at the DC input, it has priority
over the USB input. Bypass USB to ground with at least
a 4.7µF capacitor.
To support USB power sources at the USB input drive
PEN2 and USUS to select between three internally set
USB-related current limits as shown in Table 1. Choose
100mA for low-power USB mode. Choose 500mA for
high-power USB mode. Choose suspend to reduce the
USB current to 0.11mA (typ) for both USB suspend
mode and unconfigured OTG mode. To comply with
the USB 2.0 specification, each device must be initially
configured for low power. After USB enumeration, the
device can switch from low power to high power if
given permission from the USB host. The MAX8671X
does not perform enumeration. It is expected that the
system communicates with the USB host and com-
mands the MAX8671X through its PEN1, PEN2, and
USUS inputs. When the load exceeds the input current
limit, SYS drops to 82mV below BAT and the battery
supplies supplemental load current.
The MAX8671X reduces the USB current limit by 5%/°C
when the die temperature exceeds +100°C. The sys-
tem load (ISYS) has priority over the charger current, so
input current is first reduced by lowering charge cur-
rent. If the junction temperature still reaches +120°C in
spite of charge current reduction, no input current is
drawn from USB; the battery supplies the entire load
and SYS is regulated below BAT by VBSREG. Note that
this on-chip thermal-limiting circuit is not related to and
operates independently from the thermistor input.
If the USB power input is not required, connect USB to
ground or leave it unconnected. When both DC and
USB inputs are powered, the DC input has priority.
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