MIC2584/2585
Micrel
up and power-down independent of the load capacitance of
each supply. See "Figure 2" of the "Timing Diagrams".
Applications Information
Output Tracking and Sequencing
Wiring the TRK pin to either OUT1 or OUT2 of the MIC2585
enables the tracking feature. The OUT1 and OUT2 pins
provide output track sensing and are wired directly to the
output (source) of the external MOSFET for Channel 1 and
Channel 2, respectively.
The MIC2585 is equipped with optional supply
settings: Tracking or Sequencing. There are many applica-
tions that require two supplies to track one another within a
specifiedmaximumpotentialdifference(ortime)duringpower-
up and power-down, such as in switching a processor on and
off. Inmanyothersystemsandapplications, supplysequenc-
ing during turn-on may be essential such as when a specific
circuit block (e.g., a system clock) requires available power
before another block of system circuitry. For either supply
configuration, the MIC2585 requires only one additional
component and can be used as an integrated solution to
traditional, andmostoftencomplex, discretecircuitsolutions.
Additionally, the two optional supply settings may be com-
bined to provide supply sequencing during start-up and
supply tracking during turn-off (see Figure 6 below). The
MIC2585guaranteessupplytrackingwithin250mVforpower-
The MIC2584/85 can also be used in systems that support
more than two supplies. Figure 7 illustrates the generic use
of two separate controllers configured to support four inde-
pendent supply rails with an associated output timing re-
sponse. ThePG(or/POR)outputofthefirstcontrollerisused
to enable the second controller. As configured, a fault condi-
tion on either V
or V
will result in all channels being
OUT1
OUT2
shut down. For systems with multiple power sequencing
requirements, the controllers’ output tracking and sequenc-
ingfeaturescanbeimplementedinordertomeetthesystem’s
timing demands.
**Q1
RSENSE1
Si4922DY (2)
0.007Ω
VOUT1
5V@5A
(SO-8)
5%
VIN1
5V
1
3
4
CLOAD1
1500µF
*D1
(8V)
C1
1µF
**Q2
Si4922DY (1)
(SO-8)
RSENSE2
0.015Ω
5%
R4
8.06kΩ
1%
VOUT2
VIN2
1
2
1.8V@2A
1.8V
3
4
CLOAD2
*D2
C2
100µF
(6V)
1µF
C4
0.022µF
24
23
1
2
R1
47kΩ
VCC1
SENSE1 VCC2
SENSE2
GATE2
3
5
R2
39.2kΩ
1%
8
ON
OUT2
9
7
TRK
FB2
11
CFILTER
CDLY
MIC2585-1
R5
10.5kΩ
1%
C5
0.01µF
22
GATE1
C3
0.022µF
12
C6
0.1µF
20
18
OUT1
FB1
R3
15.8kΩ
1%
GND
13
Undervoltage (OUT1) = 4.4V
Undervoltage (OUT2) = 1.5V
Circuit Breaker Response Time = 5ms
Sequenced Output Delay = 20ms
*Diodes are BZX84C(x)V(x)
**Si4922DY is a dual Power MOSFET
Additional pins omitted for clarity
Figure 6. Output Sequencing/Tracking Combination
MIC2584/2585
18
March 2005
MICREL [ MICREL SEMICONDUCTOR ]
