CDH2D09 datasheet(39/44 Pages) MAXIM

39 / 44 page

PMIC with Integrated Charger and

Smart Power Selector for Handheld Devices

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USB/DC OVLO

Overvoltage lockout (OVLO) prevents an input supply

from being used when its voltage exceeds the operat-

ing range. Both USB and DC withstand input voltages

up to 14V. When the USB voltage is greater than the

USB OVLO threshold (6.9V typ), the USB input is dis-

connected from SYS, and UOK goes high impedance.

When the DC voltage is greater than the DC OVLO

threshold (6.9V typ), the DC input is disconnected from

SYS, and DOK goes high impedance. In addition, when

both DC and USB are in OVLO, the battery charger is

disabled, and BAT is connected to SYS through the

internal system load switch. REG1–REG4 are allowed to

operate from the battery when USB and DC are in over-

voltage lockout. The VL supply remains active in OVLO.

REG5 is intended to power the system USB transceiver

circuitry, which is only active when USB power is avail-

able. A valid source must be present on either the USB

or DC input for REG5 to enable.

SYS UVLO

A UVLO circuit monitors the voltage from SYS to

ground (VSYS). When VSYS falls below VUVLO_SYS (2.5V

typ), REG1–REG5 are disabled. VUVLO_SYS has a

100mV hysteresis. The VL supply remains active in SYS

UVLO.

REG4/REG5 UVLO

A UVLO circuit monitors the PV4 and PV5 LDO power

inputs. When the PV_ voltage is below 1.6V, it is invalid

and the LDO is disabled.

Thermal Limiting and Overload Protection

The MAX8671X is packaged in a 5mm x 5mm x 0.8mm

40-pin thin QFN. Table 7 shows the thermal character-

istics of this package. The MAX8671X has several

mechanisms to control junction temperature in the

event of a thermal overload.

Smart Power Selector Thermal-Overload Protection

The MAX8671X reduces the USB and DC current limits

by 5%/°C when the die temperature exceeds +100°C.

The system load (ISYS) has priority over the charger

current, so input current is first reduced by lowering

charge current. If the junction temperature still reaches

+120°C in spite of charge-current reduction, no input

current is drawn from USB and DC; the battery supplies

the entire load and SYS is regulated 82mV (VBSREG)

below BAT. Note that this on-chip thermal-limiting cir-

cuit is not related to and operates independently from

the thermistor input.

Regulator Thermal-Overload Shutdown

The MAX8671X disables all regulator outputs (except

VL) when the junction temperature rises above +165°C,

allowing the device to cool. When the junction tempera-

ture cools by approximately 15°C, the regulators

resume the state indicated by the enable input (EN)

by repeating their soft-start sequence. Note that this

thermal-overload shutdown is a fail-safe mechanism;

proper thermal design should ensure that the junction

temperature of the MAX8671X never exceeds the

absolute maximum rating of +150°C.

Battery Charger Thermistor Input (THM)

The THM input connects to an external negative tem-

perature coefficient (NTC) thermistor to monitor battery

or system temperature. Charging is suspended when

the thermistor temperature is out of range. Additionally,

the charge timers are suspended and charge status

indicators report that the charger is in thermistor sus-

pend (CST[1:2] = 01). When the thermistor comes back

into range, charging resumes and the charge timer

continues from where it left off. Table 8 shows THM

temperature limits for various thermistor material con-

stants. If the battery temperature monitor is not

required, bias THM midway between VL and AGND

with a resistive divider—100k

Ω ±5% resistors are rec-

ommended. Biasing THM midway between VL and

AGND bypasses this function.

SINGLE-LAYER PCB

MULTILAYER PCB

Continuous

Power

Dissipation

1777.8mW

Derate 22.2mW/°C

above +70°C

2857.1mW

Derate 35.7mW/°C

above +70°C

θJA

45°C/W

28°C/W

θJC

1.7°C/W

Table 7. 5mm x 5mm x 0.8mm Thin QFN

Thermal Characteristics

θJA is specified according to the JESD51 standard.

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