CDH2D09 datasheet(38/44 Pages) MAXIM

38 / 44 page

PMIC with Integrated Charger and

Smart Power Selector for Handheld Devices

______________________________________________________________________________________

Active Discharge in Shutdown

Each MAX8671X regulator (REG1–REG5) has an inter-

nal 1k

Ω resistor that discharges the output capacitor

when the regulator is off. The discharge resistors

ensure that the load circuitry powers down completely.

The internal discharge resistors are connected when a

regulator is disabled and when the device is in UVLO

with an input voltage greater than 1.0V. With an input

voltage less than 1.0V, the internal discharge resistors

are not activated.

Undervoltage and Overvoltage Lockout

USB/DC UVLO

Undervoltage lockout (UVLO) prevents an input supply

from being used when its voltage is below the operat-

ing range. When the USB voltage is less than the USB

UVLO threshold (4.0V typ), the USB input is discon-

nected from SYS, and UOK goes high impedance.

When the DC voltage is less than the DC UVLO thresh-

old (4.0V typ), the DC input is disconnected from SYS,

and DOK goes high impedance. In addition, when both

USB and DC are in UVLO, the battery charger is dis-

abled, and BAT is connected to SYS through the inter-

nal system load switch. REG1–REG4 are allowed to

operate from the battery without power at USB or DC.

REG5 is intended to power the system USB transceiver

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

able. Therefore, a valid source must be present on

either the USB or DC input for REG5 to enable.

UNPLUG

EVENT

VUSB

3.5V

HIGH-Z

UNPLUGGING USB WITH NOTHING TO DISCHARGE CUSB (VBAT = 3.3V). V5 SET FOR 3.3V

IF VBAT

≥ 3.4V, VPV5 WILL REGULATE TO 3.3V

IF VBAT

≤ 3.4V, VPV5 WILL BE SLIGHTLY LESS

THAN VBAT (DROPOUT)

VUOK

tDDREG5 = 120

μs (typ)

RAPID DISCHARGE UNTIL VUSB DECAYS

TO THE HIGHER OF 3.5V OR VBAT + 5OmV

SLOW DISCHARGE AS THE MAX8671X

DRAWS USB QUIESCENT CURRENT

Figure 13. REG5 Disable Detail

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