SMS64
Preliminary
APPLICATIONS INFORMATION
VOLTAGE MONITOR
Figure 3 shows a block diagram of a voltage
monitor. The curved resistive element is a symbolic
representation of a non-volatile DAC. When using the
SMX3200 (dongle) and GUI software the threshold
level that is selected is programmed into the SMS64,
effectively adjusting the output of the DAC to the
requested threshold detection level. The internal
detection circuit resolution is 8-bits and the threshold
detection range is 0.9V to 6.0V. This allows adjusting
the programmable threshold voltage (V
PTH
) in 20mV
increments.
In applications where the voltage to be monitored
is outside the standard range, or is even a negative
voltage, the ‘naked input’ option can be selected. This
will effectively disconnect the DAC from ground
making the VCC and VM high impedance inputs to the
DAC. With this option selected the input is directly
compared to the internal reference voltage of 0.5V.
This will require the use of an external resistor divider
circuit. If this option is selected, the user must insure
that the external resistors will not allow the VCC or VM
inputs to exceed the recommended operating ranges.
The comparator has two mux’ed voltage inputs,
VCC and VM.
The VCC inputs are used as
‘precondition qualifiers’ (No fault conditions exist)
before the SMS64 is ready to begin any power-on
sequence. Once the sequence has commenced the
mux will automatically switch the comparator to the
VM input. {When using the GUI for the SMS64 this
option is on the channel settings tab and located in the
block designated ‘triggers’}
The VCC inputs are also used as the supply input
for the SMS64. Internally all of the VCC inputs are
diode-OR’ed and the highest VCC input will effectively
become the SMS64 VDD supply. If the VCC input is
not selected as a precursor to power-on, it can be tied
to the corresponding VM input, left open or be tied to
one of the other VCC inputs
The output of the comparator is programmable to
generate either an over-voltage or under-voltage
signal.
PUP OUTPUTS
The primary function of the PUP outputs is to turn-
on or switch external power sources; for example,
turning on low drop-out regulators or DC-to-DC
converters or by providing a high-side drive output to a
MOSFET (Figure 4)
Each PUP output can be programmed as active
high or active low. If active low, the SMS64 will pull
the PUP output to GND in its active state. An external
pull-up resistor must be tied to the PUP output.
If active high is selected, an inactive PUP output
will be pulled low. Asserting the PUP output will
release the open drain output, necessitating an
external pull-up resistor. When the PUP outputs are
configured as active high or active low they must not
be pulled-up to a potential higher than VDD_CAP.
The PUP output can also be configured as a high-
side driver that can be used to turn on the gate of
an external MOSFET. The gate voltage for all PUP
outputs can be programmed to either 10.5V or 14.5V.
Input Select
Input Select
UV/OV
A
UV/OV
B
UV/OV
C
-
V
REF
+
'naked' input
select
UV/OV
VCC
VM
NV-DAC
UV/OV
D
UV/OV
E
UV/OV
F
Delay 'up'
Delay 'dn'
Highside Driver
Active High
Active Low
PUP
X
Figure 3. Voltage Monitor Diagram
Figure 4. PUP Configuration Diagram
Summit Microelectronics, Inc
2060 2.22 10/09/03
10
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
