MIC2085/MIC2086
Single Channel Hot Swap Controllers
General Description
The MIC2085 and MIC2086 are single channel positive
voltage hot swap controllers designed to allow the safe
insertion of boards into live system backplanes. The
MIC2085and MIC2086 are available in 16-pin and 20-pin
QSOP packages, respectively. Using a few external
components and by controlling the gate drive of an
external N-Channel MOSFET device, the MIC2085/86
provide inrush current limiting and output voltage slew rate
control in harsh, critical power supply environments.
Additionally, a circuit breaker function will latch the output
MOSFET off if the current limit threshold is exceeded for a
programmed period of time. The devices’ array of features
provide a simplified yet robust solution for many network
applications in meeting the power supply regulation
requirements and affords protection of critical downstream
devices and components.
Data sheets and support documentation can be found on
Micrel’s web site at
www.micrel.com.
•
Operating temperature range –40°C to 85°C
•
Active current regulation limits inrush current
independent of load capacitance
•
Programmable inrush current limiting
•
Analog foldback current limiting
•
Electronic circuit breaker
•
Dual-level overcurrent fault sensing
•
Fast response to short circuit conditions (< 1µs)
•
Programmable output undervoltage detection
•
Undervoltage lockout protection
•
Power-on reset (MIC2085/86) and power-good
(MIC2086) status outputs
•
/FAULT status output
•
Driver for SCR crowbar on overvoltage
Applications
•
•
•
•
•
•
RAID systems
Cellular base stations
LAN servers
WAN servers
InfiniBand™ Systems
Industrial high side switching
Features
•
MIC2085: Pin for pin functional equivalent to the
LTC1642
•
2.3V to 16.5V supply voltage operation
•
Surge voltage protection to 33V
Typical Application
InfiniBand is a trademark of InfiniBand Trade Association
PowerPAK is a trademark of Vishay Intertechnology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
May 2006
M9999-050406
(408) 955-1690
Micrel, Inc.
MIC2085/2086
Ordering Information
Part Number
Standard
MIC2085-xBQS
Pb-Free
MIC2085-xYQS
x = J, 95mV
x = K, 150mV*
x = L, 200mV*
x = M, Off
x = J, 95mV
x = K, 150mV*
x = L, 200mV*
x = M, Off
NA
16-Pin QSOP
Fast Circuit Breaker Threshold
Discharge Output
Package
MIC2086-xBQS
MIC2086-xYQS
Yes
20-Pin QSOP
* Contact factory for availability.
Pin Configuration
MIC2085
16-Pin QSOP (QS)
MIC2086
20-Pin QSOP (QS)
Pin Description
Pin Number
MIC2086
1
Pin Number
MIC2085
1
Pin Name
CRWBR
Pin Function
Overvoltage Timer and Crowbar Circuit Trigger: A capacitor connected to this
pin, sets the timer duration for which an overvoltage condition will trigger an
external crowbar circuit. This timer begins when the OV input rises above its
threshold as an internal 45µA current source charges the capacitor. Once the
voltage reaches 470mV, the current increases to 1.5mA.
Current Limit Response Timer: A capacitor connected to this pin defines the
period of time (t
OCSLOW
) in which an overcurrent event must last to signal a fault
condition and trip the circuit breaker. If no capacitor is connected, then t
OCSLOW
defaults to 5µs.
Power-On Reset Timer: A capacitor connected between this pin and ground
sets the start-up delay (t
START
) and the power-on reset interval (t
POR
). When VCC
rises above the UVLO threshold, the capacitor connected to CPOR begins to
charge. When the voltage at CPOR crosses 1.24V, the start-up threshold
(V
START
), a start cycle is initiated if ON is asserted while capacitor CPOR is
immediately discharged to ground. When the voltage at FB rises above VFB,
capacitor CPOR begins to charge again. When the voltage at CPOR rises above
the power-on reset delay threshold (VTH), the timer resets by pulling CPOR to
ground, and /POR is deasserted. If CPOR = 0, then t
START
defaults to 20µs.
2
2
CFILTER
3
3
CPOR
May 2006
2
M9999-050406
(408) 955-1690
Micrel, Inc.
MIC2085/2086
Pin Description (Cont.)
Pin Number
MIC2086
4
Pin Number
MIC2085
4
Pin Name
ON
Pin Function
ON Input: Active high. The ON pin, an input to a Schmitt-triggered comparator
used to enable/disable the controller, is compared to a V
TH
reference with
100mV of hysteresis. Once a logic high is applied to the ON pin (V
ON
> 1.24V), a
start-up sequence is initiated as the GATE pin starts ramping up towards its final
operating voltage. When the ON pin receives a low logic signal (V
ON
< 1.14V),
the GATE pin is grounded and /FAULT is high if VCC is above the UVLO
threshold. ON must be low for at least 20µs in order to initiate a start-up
sequence. Additionally, toggling the ON pin LOW to HIGH resets the circuit
breaker.
Power-On Reset Output: Open drain N-Channel device, active low. This pin
remains asserted during start-up until a time period t
POR
after the FB pin voltage
rises above the power-good threshold (VFB). The timing capacitor CPOR
determines t
POR
. When an output undervoltage condition is detected at the FB
pin, /POR is asserted for a minimum of one timing cycle, t
POR
. The /POR pin has
a weak pull-up to VCC
Power-Good Output: Open drain N-Channel device, active high. When the
voltage at the FB pin is lower than 1.24V, the PWRGD output is held low. When
the voltage at the FB pin is higher than 1.24V, then PWRGD is asserted. A pull-
up resistor connected to this pin and to VCC will pull the output up to VCC. The
PWRGD pin has a weak pull-up to VCC.
Circuit Breaker Fault Status Output: Open drain N-Channel device, active low.
The /FAULT pin is asserted when the circuit breaker trips due to an overcurrent
condition. Also, this pin indicates undervoltage lockout and overvoltage fault
conditions. The /FAULT pin has a weak pull-up to VCC.
Power-Good Threshold Input: This input is internally compared to a 1.24V
reference with 3mV of hysteresis. An external resistive divider may be used to
set the voltage at this pin. If this input momentarily goes below 1.24V, then /POR
is activated for one timing cycle, t
POR
, indicating an output undervoltage
condition. The /POR signal de-asserts one timing cycle after the FB pin exceeds
the power-good threshold by 3mV. A 5µs filter on this pin prevents glitches from
inadvertently activating this signal.
Ground Connection: Tie to analog ground
OV Input: When the voltage on OV exceeds its trip threshold, the GATE pin is
pulled low and the CRWBR timer starts. If OV remains above its threshold long
enough for CRWBR to reach its trip threshold, the circuit breaker is tripped.
Otherwise, the GATE pin begins to ramp up one POR timing cycle after OV
drops below its trip threshold.
Uncommitted Comparator’s Open Drain Output.
Comparator’s Non-Inverting Input.
Comparator’s Inverting Input.
Discharge Output: When the MIC2086 is turned off, a 550Ω internal resistor at
this output allows the discharging of any load capacitance to ground.
Reference Output: 1.24V nominal. Tie a 0.1µF capacitor to ground to ensure
stability.
Gate Drive Output: Connects to the gate of an external N-Channel MOSFET. An
internal clamp ensures that no more than 13V is applied between the GATE pin
and the source of the external MOSFET. The GATE pin is immediately brought
low when either the circuit breaker trips or an undervoltage lockout condition
occurs.
5
5
/POR
6
NA
PWRGD
7
6
/FAULT
8
7
FB
9, 10
11
8
9
GND
OV
12
13
14
15
16
17
10
11
12
Na
13
14
COMPOUT
COMP+
COMP-
DIS
REF
GATE
May 2006
3
M9999-050406
(408) 955-1690
Micrel, Inc.
MIC2085/2086
Pin Description (Cont.)
Pin Number
MIC2086
18
Pin Number
MIC2085
15
Pin Name
SENSE
Pin Function
Circuit Breaker Sense Input: A resistor between this pin and VCC sets the
current limit threshold. Whenever the voltage across the sense resistor exceeds
the slow trip current limit threshold (V
TRIPSLOW
), the GATE voltage is adjusted to
ensure a constant load current. If V
TRIPSLOW
(48mV) is exceeded for longer than
time period t
OCSLOW
, then the circuit breaker is tripped and the GATE pin is
immediately pulled low. If the voltage across the sense resistor exceeds the fast
trip circuit breaker threshold, V
TRIPFAST
, at any point due to fast, high amplitude
power supply faults, then the GATE pin is immediately brought low without delay.
To disable the circuit breaker, the SENSE and VCC pins can be tied together.
The default V
TRIPFAST
for either device is 95mV. Other fast trip thresholds are
available: 150mV, 200mV, or OFF (V
TRIPFAST
disabled). Please contact factory for
availability of other options.
19, 20
16
VCC
Positive Supply Input: 2.3V to 16.5V. The GATE pin is held low by an internal
undervoltage lockout circuit until VCC exceeds a threshold of 2.18V.If VCC
exceeds 16.5V, an internal shunt regulator protects the chip from VCC and
SENSE pin voltages up to 33V.
May 2006
4
M9999-050406
(408) 955-1690
Micrel, Inc.
MIC2085/2086
Absolute Maximum Ratings
(1)
(All voltages are referred to GND)
Supply Voltage (V
CC
)....................................... –0.3V to 33V
SENSE Pin ........................................... –0.3V to V
CC
+ 0.3V
GATE Pin ........................................................ –0.3V to 22V
ON, DIS, /POR, PWRGD, /FAULT,
COMP+, COMP-, COMPOUT......................... –0.3V to 20V
CRWBR, FB, OV, REF...................................... –0.3V to 6V
Maximum Currents
Digital Output Pins ......................................................10mA
(/POR, /FAUTL, PWRGD, COMPOUT)
DIS Pin ........................................................................30mA
EDS Rating
Human Body Model ................................................. 2kV
Machine Model ......................................................200V
Operating Ratings
(2)
Supply voltage (V
CC
) .................................... 2.3V to +16.5V
Operating Temperature Range ................... –40°C to +85°C
Junction Temperature (T
J
) ......................................... 125°C
Package Thermal Resistance R
θ(JA)
16-pin QSOP ...................................................112°C/W
20-pin QSOP .....................................................91°C/W
Electrical Characteristics
(3)
V
CC
= 5.0V; T
A
= 25°C, unless otherwise noted.
Bold
indicates specifications over the full operating temperature range of
–40°C to +85°C.
Symbol
V
CC
I
CC
V
UV
V
UVHYST
V
FB
V
FBHYST
V
OV
∆V
OV
V
OVHYST
I
OV
V
TH
I
CPOR
I
TIMER
V
CR
∆V
CR
I
CR
Parameter
Supply Voltage
Supply Current
Undervoltage Lockout
Threshold
UV Lockout Hysteresis
FB (Power-Good) Threshold
Voltage
FB Hysteresis
OV Pin Threshold Voltage
OV Pin Threshold Voltage Line
Regulation
OV Pin Hysteresis
OV Pin Current
POR Delay and Overcurrent
(CFILTER) Timer Threshold
Power-On Reset Timer Current
Current Limit /Overcurrent
Timer Current (CFILTER)
CRWBR Pin Threshold Voltage
CRWBR Pin Threshold Voltage
Line Regulation
CRWBR Pin Current
V
CPOR
, V
CFILTER
rising
Timer on
Timer off
Timer on
Timer off
2.3V < V
CC
< 16.5V
2.3V < V
CC
< 16.5V
CRWBR On, V
CRWBR
= 0V
CRWBR On, V
CRWBR
= 2.1V
CRWBR Off, V
CRWBR
= 1.5V
V
TRIP
= V
CC
= V
SENSE
2.3V
≤
V
CC
≤
16.5V
V
TRIPSLOW
V
TRIPFAST
x=J
x=K
x=L
–60
1.19
–2.5
–30
445
1.24
–2.0
5
–20
2.5
470
4
–45
–1.5
3.3
48
95
150
200
OV pin rising
2.3V < V
CC
< 16.5V
1.19
FB rising
1.19
V
CC
rising
V
CC
falling
2.05
1.85
Condition
Min
2.3
1.6
2.18
2.0
180
1.24
3
1.24
5
3
0.2
1.29
–1.5
–15
495
15
–30
–1.0
55
110
1.29
15
1.29
Typ
Max
16.5
2.5
2.28
2.10
Units
V
mA
V
V
mV
V
mV
mV
mV
mV
µA
V
µA
mA
µA
mA
mV
µA
mA
µA
mA
mA
mV
mV
mV
mV
V
TRIP
Circuit Breaker Trip Voltage
(Current Limit Threshold)
40
80
May 2006
5
M9999-050406
(408) 955-1690
PCB Design
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