MIC2591B-2YTQ Micrel Inc, MIC2591B-2YTQ Datasheet - Page 17

• Manufacturer Part Number: MIC2591B-2YTQ
• Description: IC CTRLR HOTPLUG PCI DUAL 48TQFP
• Manufacturer: Micrel Inc
• Type: Hot-Swap Controllerr

Specifications of MIC2591B-2YTQ

• Applications: General Purpose, PCI Express
• Internal Switch(s): No
• Voltage - Supply: 3.3V, 12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-1098

March 2005
Functional Description
Hot Swap Insertion
When circuit boards are inserted into systems carrying live
supply voltages (“hot-plugged”), high inrush currents often
result due to the charging of bulk capacitance that resides
across the circuit board’s supply pins. This transient inrush
current can cause the system’s supply voltages to temporarily
go out of regulation, causing data loss or system lock-up. In
more extreme cases, the transients occurring during a hot-
plug event may cause permanent damage to connectors or
on-board components.
The MIC2591B addresses these issues by limiting the in-
rush currents to the load (PCI Express Board), and thereby
controlling the rate at which the load’s circuits turn-on. In
addition to this inrush current control, the MIC2591B offers
input and output voltage supervisory functions and current
limiting to provide robust protection for both the system and
circuit board.
System Interface
The MIC2591B employs two system interfaces: the hard-
ware Hot-Plug Interface (HPI) and the System Management
Interface (SMI). The HPI includes ON[A/B], AUXEN[A/B],
as well as /FAULT[A/B]; the SMI consists of SDA, SCL,
and /INT, whose signals conform to the levels and timing of
the SMBus specifi cation. The MIC2591B can be operated
exclusively from the SMI, or can employ the HPl for power
control while continuing to use the SMI for access to all but
the power control registers.
In addition to the basic power control features of the MIC2591B
accessible by the HPI, the SMI also gives the host access to
the following information from the part:
When using the System Management Interface for power
control, do not use the Hot-Plug Interface. Conversely, when
using the Hot-Plug Interface for power control, do not execute
power control commands over the System Management
Interface bus (all other register accesses via the SMI bus
remain permissible while in the HPI control mode). When
utilizing the SMI exclusively, the HPI input pins (ON[A/B],
AUXEN[A/B], and /FORCE_ON[A/B] should be confi gured
as shown below in Figure 6 (Disabling HPI when SMI control
• Output voltage and current from each supply.
• Fault conditions occurring on each supply.
• GPI_[A0/B0] pin status.
/INT
Figure 6. Input Pin Confi guration for Disabling HPI/SMI Control
100k
100k
V
Disabling SMI when
HPI Control is used
STBY
100k
47
48
37
39
40
41
SCL
SDA
/INT
A2
A1
A0
MIC2591B
17
is used). This confi guration safeguards the power slots in the
event that the SMBus communication link is disconnected
for any reason.
Additionally, when utilizing the HPI exclusively, the SMBus
(or SMI) will be inactive if the input pins (SDA, SCL, A0, A1,
and A2) are confi gured as shown in Figure 6 below (Disabling
SMI when HPI Control is used).
Power Stability and Power-On Reset
The MIC2591B utilizes VSTBY[A/B] as the main supply input
source. VSTBY[A/B] is required for proper operation of the
MIC2591B’s SMBus and registers and must be applied at
all times. To ensure that the MIC2591B controller operates
properly, the V
the undervoltage lockout (UVLO) threshold once applied.
Suffi cient input bulk capacitance should be used to prevent
the supply from "drooping", causing VSTBY[A/B] to fall below
the UVLO threshold. Also, decoupling capacitors should be
placed at each of the MIC2591B inputs in order to fi lter high
frequency noise transients.
V
MAIN supply inputs of 12V
(POR) cycle is initiated after VSTBY[A/B] rises above its
UVLO threshold and remains valid at that voltage for 250µs.
All internal registers are cleared after POR. If VSTBY[A/B] is
recycled, the MIC2591B enters a new power-on-reset cycle.
The SMBus is ready for access at the end of the POR cycle
(250µs after VSTBY[A/B] is valid). During t
remain off. In most applications, the total POR interval will
consist of the time required to charge the V
pass) capacitance to the UVLO threshold plus the internal
t
POR interval:
where C
I
to charge the capacitance.
to charge the capacitance.
Power-Up Cycle
Enabling the GATE output
When a slot's MAIN supplies are off, the 12VGATE pin is held
high with an internal pull-up. Similarly, the 3VGATE pin is
internally held low. When the MAIN supplies of the MIC2591B
POR
CHARGE(STBY)
CHARGE(STBY)
CHARGE(STBY)
t
STBY
STBY
STBY
POR_TOTAL(µS)
. The following equation is used to approximate the total
100k
must be the fi rst supply input applied followed by the
must be the fi rst supply input applied followed by the
STBY
STBY
STBY
V
100k
STBY
=
is the V
is the V
Disabling HPI when
SMI Control is used
STBY
STBY
STBY





is the current supplied by the V





43
28
45
42
44

C
9
STBY(µF)
input must be stable and remain above
input must be stable and remain above
AUXENB
ONA
ONB
STBY
STBY
STBY
AUXENA
/FORCE_ONA
/FORCE_ONB
MIC2591B
I
CHARGE(STBY)
input bulk bypass capacitance and
input bulk bypass capacitance and
 V
IN
ULVO(STBY)
and 3V
(A)
IN
. A Power-On Reset







10
POR
STBY
STBY
STBY

6
, all outputs
STBY
STBY
STBY
M9999-033105





 t
input (by-
input (by-
POR
source
source
(µS)