SMB218 View Datasheet(PDF) - Summit Microelectronics

Part Name

Description

Manufacturer

SMB218

Six-Channel Programmable DC-DC Power Managers with Battery Charger

Summit Microelectronics 

PLEASE NOTE: The SMB118 has entered End-of-Life.

SMB118/218

APPLICATIONS INFORMATION

DEVICE OPERATION

POWER SUPPLY

The SMB118 and SMB218 can be powered from an

input voltage between +2.7 and +6 volts applied

between the VBATT pin and ground. The input voltage

applied to the VBATT pin is filtered by an external filter

capacitor attached between the VDD_CAP pin and

ground; this filtered voltage is then used as an internal

VDD supply. The VDD_CAP node is monitored by an

Under-Voltage Lockout (UVLO) circuit, which prevents

the outputs from turning on when the voltage at this

node is less than the UVLO threshold.

When the voltage on the DOCK_DC input exceeds that

on the VBATT input the VBATT pin goes into a high

impedance state and no longer powers the devices,

and the DOCK_DC pin becomes the new power input.

SHUTDOWN

The SMB118 and SMB218 are equipped with a

shutdown pin that disconnects power from the devices

and reduces the current consumption to 0.6µA when

asserted. When the SHDN pin is pulled high, all outputs

will be disabled and the SMB118 and SMB218 will not

respond to I2C commands.

To exit the shutdown mode the SHDN pin can be pulled

high, or voltage can be applied to the DOCK_DC input.

When voltage is present on the DOCK_DC input the

device will exit the shutdown mode and operate

normally.

POWER-ON/OFF CONTROL

Sequencing can be initiated: automatically, by a volatile

I2C Power on command, or by asserting the PWREN

pin. When the PWREN pin is programmed to initiate

sequencing, it can be level or edge triggered. The

PWREN input has a programmable de-bounce time of

100, 50, or 25ms. The de-bounce time can also be

disabled.

When configured as a push-button enable, the PWREN

must be low longer than the debounce time before

sequencing can commence, and pulled low for the

same period to disable the channels.

When a software power off command is written to the

volatile memory the system will be powered off

regardless of the state of the PWREN pin.

ENABLE

Each output can be enabled and disable by an enable

signal. The enable signal is can be provided from either

the PWREN pin or by the contents of the enable

register.

When enabling a channel from the enable register, the

register contents default state must be set so that the

output will be enabled or disabled following a POR

(power on reset). The default state is programmable.

CASCADE SEQUENCING

Each channel on the SMB118 and SMB218 may be

placed in any one of 6 unique sequence positions, as

assigned by the configurable non-volatile register

contents. The SMB118 and SMB218 navigate between

each sequence position using a feedback-based

cascade-sequencing circuit. Cascade sequencing is the

process in which each channel is continually compared

against a programmable reference voltage until the

voltage on the monitored channel exceeds the

reference voltage, at which point an internal sequence

position counter is incremented and the next sequence

position is entered. In the event that a channels enable

input is not asserted when the channel is to be

sequenced on, that sequence position will be skipped

and the channel in the next sequence position will be

enabled.

Figure 4 – Power on sequencing waveforms.

Time = 4ms/devision, Scale = 1V/devision

Ch 1 = 3.3V output (Yellow trace)

Ch 2 = 2.5V output (Blue trace)

Ch 3 = 1.8V output (Purple trace)

Ch 4 = 1.2V output (Green trace)

POWER ON/OFF DELAY

There is a programmable delay between when

channels in subsequent sequence positions are

enabled. The delay is programmable at 50, 25, 12.5

and 1.5ms intervals. This delay is programmable for

each of the four sequence positions.

MANUAL MODE

The SMB118 and SMB218 provide a manual power-on

mode in which each channel may be enabled

Summit Microelectronics, Inc

2107 3.0 10/15/2008

18

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