SMS64
Preliminary
APPLICATIONS INFORMATION (CONTINUED)
Channel A
Applications Example
Sequenced; Sequence Position 2; Power-On
A simple application example is shown in Figure 8.
Three voltages are provided by a motherboard, +5V,
+3.3V, and +1.8V. The +5V and +3.3V supplies are
switched on through series MOSFETS and applied to
the application circuit. The +1.8V supply will drive an
LDO, supplying +1.2V to the application circuit. The
application requires that the power supplies sequence
in the following order: +1.2V, +3.3V, +5.0V. As these
supplies are sequenced on, RST_A# is cleared after
the +1.2V supply has reached its under-voltage
threshold. RST_B# is not cleared until the +3.3V and
+5.0V supplies have reached their under-voltage
threshold. After the supplies have sequenced on, a
10% under-voltage on the +1.2V supply will trigger
RSTA#. Similarly, a 10% under-voltage on the +3.3V
supply will trigger RSTB#. The devices driven by the
application circuit require that if a 10% under-voltage
occurs on the +5.0V supply, the SMS64 will generate
an IRQ#. A 10% over-voltage on any supply will
trigger both RSTA# and RSTB#. This application also
requires that the power supplies are sequenced off in
the reverse order that they were sequenced on. The
power supply sequencing is controlled by toggling the
PWR_ON/OFF pin. With these requirements, the
SMS64 is configured as follows:
Delay(tDPONA) = 50ms; Power-Off Delay(tDPOFFA) =
50ms;
Under-voltage; Programmable Threshold(VPTHA) =
4.50V
Channel B
Sequenced; Sequence Position 1; Power-On
Delay(tDPONB) = 25ms; Power-Off Delay(tDPOFFB) =
25ms;
Under-voltage; Programmable Threshold(VPTHB) =
2.96V
Channel C
Sequenced; Sequence Position 0; Power-On
Delay(tDPONC) = 50ms; Power-Off Delay(tDPOFFC) =
100ms;
Under-voltage; Programmable Threshold(VPTHC) =
1.06V
Channel D
Not Sequenced; Sequence Position null (7);
Over-voltage; Programmable Threshold(VPTHD) =
5.50V
+3.3V
+3.3V
V+
OUT
+1.8V
+1.2V
ON/OFF
SET
GND
VMC
VMF
SMS64
IRQ#
RSTA#
RSTB#
+5.0V
+5.0V
Figure 8 – Simple Applications Example
Summit Microelectronics, Inc
2060 2.22 10/09/03
16
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
