CDH2D09 datasheet(26/44 Pages) MAXIM

26 / 44 page

PMIC with Integrated Charger and

Smart Power Selector for Handheld Devices

______________________________________________________________________________________

USB Power-OK Output (

UOK)

As shown Figure 3, the USB power-OK output (UOK) is

an active-low open-drain output. The UOK output pulls

low when the voltage from USB to AGND (VUSB) is

between VUSBH (typically 6.9V) and VUSBL (typically

4.0V).

The USB power-OK circuitry remains active in thermal

overload and USB suspend. If the USB power-OK out-

put feature is not required, connect UOK to ground or

leave unconnected.

USB Suspend (USUS)

As shown in Table 1, driving USUS high suspends the

DC or USB inputs if they are configured as a USB

power input. The suspend current is 110µA when USUS

is driven high allowing the MAX8671X to comply with

the USB 1.1/2.0 specification for USB suspend as well

as the USB OTG specification for an unconfigured

device. If an external input (USB or DC) is connected to

the MAX8671X and suspended, the SYS node is sup-

ported by the battery. The DOK, UOK, and VL circuits

remain active in USB suspend mode.

A common assumption is that REG5 is disabled in USB

suspend. This is not true. REG5 is not affected by the

USB suspend mode. While in suspend, a USB device

must provide the 3.3V termination to the USB trans-

ceivers’ pullup resistors. This 3.3V termination can

come from the MAX8671X’s VL output or REG5. Both

remain enabled in USB suspend.

DC Power Input (DC)

DC is a current-limited power input that supplies the

system (SYS) up to 1A. The DC-to-SYS switch is a lin-

ear regulator designed to operate in dropout. This lin-

ear regulator prevents the SYS voltage from exceeding

5.3V. As shown in Table 1, DC supports four different

current limits that are set with the PEN1, PEN2, and

USUS digital inputs. These current limits are ideally

suited for use with AC-to-DC wall adapters and USB

power. The operating voltage range for DC is 4.1V to

6.6V, but it can tolerate up to 14V without damage.

When the DC input voltage is below the undervoltage

threshold (VDCL, 4V typ), it is considered invalid.

Similarly, if the DC voltage is above the overvoltage

threshold (VDCH, 6.9V typ), it is considered invalid.

When the DC voltage is below the battery voltage, it is

considered invalid. The DC power input is disconnect-

ed when the DC voltage is invalid. As shown in Table 1,

when power is available at the DC input, it has priority

over the USB input. Bypass DC to ground with at least

a 4.7µF capacitor.

UOK

VUSBL

4.0V RISING (typ)

500mV HYST

VUSBH

6.9V RISING (typ)

400mV HYST

USB

UNDERVOLTAGE

USB

OVERVOLTAGE

AGND

MAX8671X

Figure 3. USB Power-OK Logic

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