SMS64 datasheet(10/24 Pages) SUMMIT

10 / 24 page

SMS64

Preliminary

Summit Microelectronics, Inc

2060 2.22 10/09/03

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 (VPTH) 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.

APPLICATIONS INFORMATION

PUP

Delay 'up'

Delay 'dn'

Input Select

UV/OV

Highside Driver

Active High

Active Low

Figure 4. PUP Configuration Diagram

REF

VCC

NV-DAC

'naked' input

select

UV/OV

Input Select

Figure 3. Voltage Monitor Diagram

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