SMM665C

Summit Microelectronics, Inc

2125 3.2 5/24/2011

2

GENERAL DESCRIPTION

The SMM665C is a highly integrated and accurate

power supply controller, monitor and sequencer. It

has the ability to automatically control, monitor and

cascade sequence up to six power supplies. Also, the

SMM665C can monitor the VDD input, the 12V input,

two general-purpose analog inputs and the internal

temperature sensor.

The SMM665C has four

operating

modes:

Power-on

sequencing

mode,

monitor mode, supply margining mode using Active

DC

Output

Control

(ADOC

sequencing mode.

Power-on sequencing can be initiated via the

PWR_ON/OFF pin or I

SMM665C will sequence the power supply channels

on in any order by activating the PUP outputs and

monitoring the respective converter voltages to ensure

cascading of the supplies. Cascade sequencing is the

ability to hold off the next sequenced supply until the

first supply reaches a programmed threshold. A

programmable sequence termination timer can be set

to disable all channels if the Power-on sequence

stalls. Once all supplies have sequenced on and the

voltages are above the UV settings, the Active DC

Control, if enabled, will bring the supply voltages to

their nominal settings.

During this mode, the

HEALTHY output will remain inactive and the RST

output will remain active.

Once the Power-on sequencing mode is complete, the

SMM665C enters monitor mode. In the monitor mode,

the SMM665C starts the ADOC control of the supplies

and adjusts the output voltage to the programmed

setting under all load conditions, especially useful for

supplies without sense lines. Typical converters have

±2% accuracy ratings for their output voltage, the

Active DC Output Control feature of the SMM665C

increases the accuracy to

±0.2% (using a ±0.1%

external voltage reference). The part also enables the

triggering of outputs by monitored fault conditions.

The 10-bit ADC cycles through all 11 channels every

2ms and checks the conversions against the

programmed threshold limits. The results can be used

to trigger RST, HEALTHY and FAULT outputs as well

as to trigger a Power-off or a Force Shutdown

operation.

While the SMM665C is in its monitoring mode, an I

command to margin the supply voltages can bring the

part into margining mode.

In margining mode the

SMM665C can margin six supply voltages in any

combination of nominal, high and low voltage settings

using the ADOC feature, all to within ±0.2% using a

±0.1% external reference. The margin high and low

voltage settings can range from 0.3V to VDD around

the converters’ nominal output voltage setting

depending on the specified margin range of the DC-

DC converter. During this mode the HEALTHY output

is always active and the RST output is always inactive

regardless of the voltage threshold limit settings and

triggers. Furthermore, the triggers for Power-off and

Force Shutdown are temporarily disabled.

The Power-off sequencing mode can only be entered

while the SMM665C is in the monitoring mode. It can

be initiated by either bringing the PWR_ON/OFF pin

inactive, through I

exceeding its programmed thresholds. Once Power-

off is initiated, it will disable the Active DC Control and

sequence the PUP outputs off in either the same or

reverse order as Power-on sequencing and monitor

the supply voltages to ensure cascading of the

supplies as they turn off. The sequence termination

timer can be programmed to immediately disable all

channels if the Power-off sequencing stalls. The RST

output will remain active throughout this mode while

the HEALTHY output remains inactive.

Figure 2 – Example Power Supply Sequencing and System Start-up Initialization using the SMM665C. Any

order of supply sequencing can be applied using the SMM665C. Power supply ordering, trimming and Active

DC control allows supply cascade sequencing, automatic level adjustment, margin testing and reset control.

2.5V

2.7V

1.8V

2.0V

1.5V

VDD (+2.7V to +5.5V)

or 12VIN ( +8V to +15V)

RST#

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