LP5550 datasheet(19/25 Pages) NSC

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Operation Description

DEVICE INFORMATION

The LP5550 is a PowerWise Interface (PWI) compliant

power management unit (PMU) for application or baseband

processors in mobile phones or other portable equipment. It

operates cooperatively with processors using National Semi-

conductor’s Advanced Power Controller (APC) to provide

Adaptive or Dynamic Voltage Scaling (AVS, DVS) which

drastically improves processor efficiencies compared to con-

ventional power delivery methods. The LP5550 consists of a

high efficiency switching DC/DC buck converter to supply the

AVS or DVS voltage domain, three LDOs for supplying the

logic, PLL, and memory, and PWI registers and logic.

OPERATION STATE DIAGRAM

The LP5550 has four operating states: Start-up, Active,

Sleep and Standby.

The Start-up state is the default state after reset. All regula-

tors are off and PWROK output is ‘0’. The device will power

up when the external enable-input is pulled high. After the

power-up sequence LP5550 enters the Active state.

In the Active state all regulators are on and PWROK-output

is ‘1’. Immediately after Start-up the output voltages are at

their default levels. LP5550 can be turned off by supplying

the Shutdown command over PWI, or by setting ENABLE

and/or RESETN to ’0’. The LP5550 can be switched to the

Sleep state by issuing the Sleep command.

In the Sleep state the core voltage regulator is off, but the

PWROK output is still ‘1’. The memory voltage regulator

(VO3) provides the programmed memory retention voltage.

LDO1 and LDO2 are on. The LP5550 can be activated from

the Sleep state by giving the Wake-up command. This re-

sumes the last programmed Active state configuration. The

device can also be switched off by giving the Shutdown

command, or by setting ENABLE and/or RESETN to ‘0’

In the Shutdown-state all output voltages are ‘0’, and

PWROK-signal is ‘0’ as well. The LP5550 can exit the

Shutdown-state if either ENABLE or RESETN is ‘0’. In either

case the device moves to the Start-up state. See the EN-

ABLE

Figure 6 shows the LP5550 state diagram. The figure as-

sumes that supply voltage to the regulator IC is in the valid

range.

20154545

FIGURE 6. LP5550 State Diagram

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