SMM605
Preliminary Information
Figure 2 – Example Power Supply Margining using the SMM605. The waveform on the left is margin low to
high from 1.6V to 2.0V and the waveform on the right is margin high to nominal from 2.0V to 1.8V. The ADOC
function guarantees the output level to be within ±0.2% maximum with a ±0.1% external reference. The
bottom waveform is the READY signal indicating margin is complete.
GENERAL DESCRIPTION
The SMM605 is capable of controlling the DC output
of up to six DC/DC Modules, switching regulators or
LDOs that use a trim/adjust pin and automatically
change the level using a unique Active DC Output
Control (ADOC
TM
). The ADOC function is
programmable over a standard 2-wire I
2
C serial data
interface and can be used to set the nominal DC
output voltage as well as the margin high and low
settings. The part actively controls the programmed
set levels to maintain tight control over load variations
and voltage drops at the point of load. The margin
range will vary depending on the supply manufacturer
and model but the normal range is 10% adjustment
around the nominal output setting. However, the
SMM605 has the capability to margin from 0.35V to
VDD. The user can set the desired voltage settings
(nominal, margin high and margin low) into the EE
memory array for the device. Then, volatile registers
are used to select one of these settings. These
registers are accessed over the I
2
C bus.
In normal operation, Active DC Output Control is set to
adjust the nominal output voltage of the converter.
Typical converter accuracy ratings range from
±2%
to
±5%
of their output voltage. Using the Active DC
Output Control feature of the SMM605 can increase
the accuracy to
±0.1%
(±0.2% Max.). This high
accuracy control of the converter output voltage is
extremely important in low voltage applications where
deviations in power supply voltage can result in lower
system performance. Active DC Output Control can
also be used for margining a supply during system test
or may be turned off by de-selecting the function in the
Control Register.
The margin high and margin low voltage settings can
range from 0.35V to VDD around the converters’
nominal output voltage setting depending on the
specified margin range of the DC-DC converter.
When the SMM605 receives the command to margin,
the Active DC Output Control will adjust the supply to
the selected margin voltage. Once the supply has
reached its margined set point, the Ready bit in the
status register will set and the READY pin will go
active. If Active DC Control is disabled, a margined
supply can return to its nominal voltage by writing to
the margin command register.
In order to obtain maximum accuracy, the SMM605
requires an external voltage reference. An external
reference with ±0.1% accuracy will enable an overall
±0.2% accuracy for the device. A configuration option
also exists so that an internal voltage reference can be
used, but with less accuracy. Total accuracy using the
internal reference is ±0.5%.
The SMM605 has additional filter pins to filter
unwanted switching regulator noise.
They are
VDD_CAP and FILT_CAP.
The SMM605 can be powered from either the 12VIN
supply pin (6V to 14V range) via an internal regulator
or the VDD supply pin (+2.7 to 5.5V range), see Figure
3.
Programming of the SMM605 is performed over the
industry standard I
2
C 2-wire serial data interface. A
status register is available to read the state of the part
and a Write Protect bit is available to prevent writing to
the configuration registers and EE memory.
Summit Microelectronics, Inc
2064 1.1 09/16/03
2
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
