MIC2085/2086
Micrel
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 MIC2085
and 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.
All support documentation can be found on Micrel’s web
site at www.micrel.com.
Features
• MIC2085: Pin for pin functional equivalent to the
LTC1642
• 2.3V to 16.5V supply voltage operation
• Surge voltage protection to 33V
• 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
Typical Application
Backplane PCB Edge
Connector Connector
V
IN
12V
Long
Pin
R1
3.3Ω
C1
1µF
3
R
SENSE
0.007Ω
1
2%
2
4
Q1
Si7884DP
(PowerPAK
TM
SO-8)
V
OUT
12V@5A
C
LOAD
220µF
Short
Pin
16
15
*R6
10Ω
R7
127kΩ
1%
V
LOGIC
GATE
COMP+
14
11
10
VCC
R5
47kΩ
R2
100kΩ
1%
4
SENSE
R10
47kΩ
R11
47kΩ
ON
/FAULT
COMPOUT
Output Signal
(Power Good)
/FAULT
R3
Medium 1.82kΩ
1%
(or Short)
Pin
R4
10kΩ
1%
6
C2
0.022µF
MIC2085
/POR
FB
5
7
PWRGD
LOGIC
CONTROLLER
/RESET
9
12
13
OV
COMP—
REF
CPOR
3
Power-On Reset
Output
R8
16.2kΩ
1%
C7
0.033µF
CRWBR
GND
8
1
Q2
2N4401
CFILTER
2
Q3
TCR22-4
GND
Long
Pin
C3
0.1µF
C4
0.1µF
C5
8200pF
C6
0.01µF
**R9
180Ω
Overvoltage (Input) = 13.3V
Undervoltage Lockout = 10.8V
Undervoltage (Output) &
Power-Good (Output) = 11.4V
POR/START-UP DELAY = 60ms
Circuit-Breaker Response Time = 500µs
*R6 is an optional component used for noise filtering
**R9 needed when using a sensitive gate SCR
InfiniBand is a trademark of InfiniBand Trade Association
PowerPAK is a trademark of Vishay Intertechnology Inc.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
January 2004
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M0235-121903
MIC2085/2086
Micrel
Ordering Information
Part Number
MIC2085-xBQS
Fast Circuit Breaker Threshold
x = J, 95mV
x = K, 150mV*
x = L, 200mV*
x = M, Off
x = J, 95mV
x = K, 150mV*
x = L, 200mV*
x = M, Off
Discharge Output
NA
Package
16-pin QSOP
MIC2086-xBQS
Yes
20-pin QSOP
*Contact factory for availability.
Pin Configuration
CRWBR 1
CFILTER 2
20 VCC
19 VCC
18 SENSE
17 GATE
16 REF
15 DIS
14 COMP–
13 COMP+
12 COMPOUT
11 OV
CRWBR 1
CFILTER 2
CPOR 3
ON 4
/POR 5
/FAULT 6
FB 7
GND 8
16 VCC
15 SENSE
14 GATE
13 REF
12 COMP–
11 COMP+
10 COMPOUT
9 OV
CPOR 3
ON 4
/POR 5
PWRGD 6
/FAULT 7
FB 8
GND 9
GND 10
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
C
POR
is immediately discharged to ground. When the voltage at FB rises
above V
FB
, capacitor C
POR
begins to charge again. When the voltage at
CPOR rises above the power-on reset delay threshold (V
TH
), the timer
resets by pulling CPOR to ground, and /POR is deasserted.
If C
POR
= 0, then t
START
defaults to 20µs.
2
2
CFILTER
3
3
CPOR
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January 2004
MIC2085/2086
Micrel
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 compara-
tor 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 (V
FB
). The timing capacitor
C
POR
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
N/A
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
January 2004
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M0235-121903
MIC2085/2086
Micrel
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.
M0235-121903
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January 2004
MIC2085/2086
Micrel
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, /FAULT, PWRGD, COMPOUT)
DIS Pin ....................................................................... 30mA
ESD 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(J-A)
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 rising
FB Hysteresis
OV Pin Threshold Voltage
OV Pin Threshold Voltage
Line Regulation
OV Pin Hysteresis
OV Pin Current
POR Delay and Overcurrent (CFILTER) V
CPOR
, V
CFILTER
rising
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
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
8
12
21–V
CC
OV pin rising
2.3V < V
CC
< 16.5V
1.19
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
mV
µA
mA
mA
mV
mV
mV
mV
V
V
V
V
TRIP
Circuit Breaker Trip Voltage
(Current Limit Threshold)
40
80
V
GS
External Gate Drive
V
GATE
– V
CC
V
CC
< 3V
5V < V
CC
< 9V
9V < V
CC
< 15.0V
4
11
4.5
9
13
13
January 2004
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M0235-121903
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