MIC2584 Datasheet, PDF (18/28 Pages) Micrel Semiconductor – Dual-Channel Hot Swap Controller/Sequencer

MIC2584/2585
Applications Information
Output Tracking and Sequencing
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
specified maximum potential difference (or time) during power-
up and power-down, such as in switching a processor on and
off. In many other systems and applications, supply sequenc-
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, and most often complex, discrete circuit solutions.
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
MIC2585 guarantees supply tracking within 250mV for power-
Micrel
up and power-down independent of the load capacitance of
each supply. See "Figure 2" of the "Timing Diagrams".
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 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. The PG (or /POR) output of the first controller is used
to enable the second controller. As configured, a fault condi-
tion on either V_OUT1 or V_OUT2 will result in all channels being
shut down. For systems with multiple power sequencing
requirements, the controllers’ output tracking and sequenc-
ing features can be implemented in order to meet the system’s
timing demands.
V_IN1
5V
V_IN2
1.8V
*D1
(8V)
*D2
(6V)
R1
47kΩ
R_SENSE1
0.007Ω
1 ^5%
**Q1
Si4922DY (2)
(SO-8)
3
4
C1
1µF
R_SENSE2
0.015Ω
1 ^5% 2
**Q2
R4
Si4922DY (1) 8.06kΩ
(SO-8)
1%
C2
1µF
24
VCC1
3
23
1
SENSE1 VCC2
4
C4
2 ^0.022µF
SENSE2
GATE2 ³
8 _ON
5
OUT2
C_LOAD1
1500µF
V_OUT1
5V@5A
V_OUT2
1.8V@2A
C_LOAD2
100µF
R2
39.2kΩ
1%
C5
0.01µF
11 _CFILTER
MIC2585-1
C6
0.1µF
12 _CDLY
GND
13
9
TRK
FB2 ⁷
GATE1 ²²
R5
10.5kΩ
1%
C3
0.022µF
OUT1 ²⁰
FB1 ¹⁸
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
R3
15.8kΩ
1%
MIC2584/2585
18
March 2005