LP3910 Datasheet, PDF (43/72 Pages) Texas Instruments – Power Management IC for Hard-Drive-Based Portable Media Players

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LP3910
SNVS481M – NOVEMBER 2006 – REVISED DECEMBER 2015
8.3.16 USB Suspend Mode
The LP3910 USB current consumption can be disabled during suspend mode through a dedicated pin
(USBSUSP). Applying a logic 1 to this pin disables the USB current path, and current is reduced to input leakage
current less than 30 µA on the USBPWR pin.
8.3.17 Setting the USB Current Limit
The USB current that is available from the USB on the VBUS wire is limited by default to 100 mA. More current
(up to 800 mA) can be negotiated through a session request protocol between host and peripheral. The USB
current limit must be signaled to the LP3910 by means of the USBISEL pin or the I_LIMIT register as indicated
below:
• If the USB current limit is 100 mA then the USB controller of the peripheral system must set the USBISEL
logic 0 or by setting the I_LIMIT register bits [D1, D0] to 2’b00.
• If the USB current limit is 500 mA, the USB controller must apply logic 1 to the USBISEL pin or change the
I_LIMIT register accordingly. Under this condition, the LP3910 allows charging with a charge current that is
determined by the charge control register, not exceeding 500 mA.
The LP3910 prevents (through internal circuitry) the charge current from exceeding the USB current limit, even if
the current setting in the Charge Control Register exceeds 500 mA.
The controller can also select a USB current limit of 800 mA through I²C that exceeds current USB spec values.
8.3.18 Control Registers
The LP3910 contains 14 user-programmable registers that configure the functionality of the individual modules
inside the device. Registers are programmed through an I²C interface and have default values that are invoked
during an internal reset. Some of the default values can be tailored to the specific needs of the system designer.
8.4 Device Functional Modes
The LP3910 can be in 3 different operating modes as shown in Figure 64:
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