General Description
MIC2587/MIC2587R
Single-Channel, Positive High-Voltage
Hot Swap Controller
Power, Connect, and Protect is a trademark of Micrel 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
October 2004
M9999-102204
(408) 955-1690
General Description
The MIC2587 and MIC2587R are single-channel positive
voltage hot swap controllers designed to provide safe
insertion and removal of boards for systems that require
live (always-powered) backplanes. These devices use few
external components and act as controllers for external N-
channel power MOSFET devices to provide inrush current
control and output voltage slew rate control. Overcurrent
fault protection is provided via programmable analog
foldback current limit circuitry equipped with a
programmable overcurrent filter. These protection circuits
combine to limit the power dissipation of the external
MOSFET to insure that the MOSFET is in its SOA during
fault conditions. The MIC2587 provides a circuit breaker
function that latches the output MOSFET off if the load
current exceeds the current limit threshold for the duration
of the programmable timer. The MIC2587R provides a
circuit breaker function that automatically attempts to
restart power after a load current fault at a low duty cycle to
prevent the MOSFET from overheating. Each device
provides either an active-HIGH (-1BM) or an active-LOW
(-2BM) "Power-is-Good" signal to indicate that the output
load voltage is within tolerance.
Data sheets and support documentation can be found on
Micrel's web site at
www.micrel.com
.
Features
MIC2587: Pin-for-pin functional equivalent to the LT1641
Operates from +10V to +80V with 100V ABS MAX operation
Industrial temperature specifications at V
CC
= +24V and
V
CC
= +48V
Programmable current limit with analog foldback
Active current regulation minimizes inrush current
Electronic circuit breaker for overcurrent fault protection
-
Output latch off (MIC2587) or
-
Output auto-retry (MIC2587R)
Fast responding circuit breaker (< 2
s) to short circuit loads
Programmable input undervoltage lockout
Fault Reporting:
Open-drain "Power-is-Good" output for enabling DC/DC
converter(s)
-
Active-HIGH:
MIC2587-1/MIC2587R-1
-
Active-LOW:
MIC2587-2/MIC2587R-2
Applications
General-purpose hot board insertion
High-voltage, high-side electronic circuit breaker
+12V/+24V/+48V Distributed Power Systems
+24V/+48V Industrial/Alarm Systems
Telecom Systems
Medical Systems
Ordering Information
Part Number
Standard Pb-Free
PWRGD Polarity
Circuit Breaker Function
Package
MIC2587-1BM
MIC2587-1YM
Active-HIGH
Latched
8 pin SOIC
MIC2587-2BM
MIC2587-2YM
Active-LOW
Latched
8 pin SOIC
MIC2587R-1BM MIC2587R-1YM
Active- HIGH
Auto-retry
8 pin SOIC
MIC2587R-2BM MIC2587R-2YM
Active-LOW
Auto-retry
8 pin SOIC
Micrel
MIC2587/MIC2587R
October 2004
2
M9999-102204
(408) 955-1690
Typical Application
MIC2587/87R Typical Application Circuit
Pin Configuration
8-pin SOIC (M)
MIC2587-1BM
MIC2587R-1BM
8-pin SOIC (M)
MIC2587-2BM
MIC2587R-2BM
Micrel
MIC2587/MIC2587R
October 2004
3
M9999-102204
(408) 955-1690
Pin Description
Pin Number
Pin Name
Pin Function
1 ON
Enable Input: When the voltage at the ON pin is higher than the V
ONH
threshold, a start cycle
is initiated. An internal current source (I
GATEON
) is activated which charges the GATE pin,
ramping up the voltage at this pin to turn on an external MOSFET. Whenever the voltage at
the ON pin is lower than the V
ONL
threshold, an undervoltage lockout condition is detected
and the I
GATEON
current source is disabled while the GATE pin is pulled low by another
internal current source (I
GATEOFF
). After a load current fault, toggling the ON pin LOW will
reset the circuit breaker then back HIGH (ON pin) will initiate another start cycle.
2 FB
Output Voltage Feedback Input: This pin is connected to an external resistor divider that is
used to sample the output load voltage. The voltage at this pin is measured against an
internal comparator whose output controls the PWRGD (or /PWRGD) signal. PWRGD (or
/PWRGD) asserts when the FB pin voltage crosses the V
FBH
threshold. When the FB pin
voltage is lower than its V
FBL
threshold, PWRGD (or /PWRGD) is de-asserted. The FB
comparator exhibits a typical hysteresis of 80mV.
The FB pin voltage also affects the MIC2587/MIC2587R's foldback current limit operation
(see the "Functional Description" section for further information).
3
PWRGD
(MIC2587-1)
(MIC2587R-1)
Active-HIGH
/PWRGD
(MIC2587-2)
(MIC2587R-2)
Active-LOW
Power-is-Good (PWRGD or /PWRGD), Open-drain Output: This pin remains de-asserted
during start up while the FB pin voltage is below the V
FBH
threshold. Once the voltage at the
FB pin rises above the V
FBH
threshold, the Power-is-Good output asserts with minimal delay
(typically
5
s).
For the (-1) options, the PWRGD output pin will be high-impedance when the FB pin voltage
is higher than V
FBH
and will pull down to GND when the FB pin voltage is less than V
FBL
.
For the (-2) options, the /PWRGD output pin will be high-impedance when the FB pin
voltage is lower than V
FBL
and will pull down to GND when the FB pin voltage is higher than
V
FBH
.
The Power-is-Good output pin is connected to an open-drain, N-channel transistor
implemented with high-voltage structures. These transistors are capable of operating with
pull-up resistors to supply voltages as high as 100V.
To use this signal as a logic control in low-voltage dc-dc conversion applications, an external
pull-up resistor between this pin and the logic supply voltage is recommended, unless an
internal pull-up impedance is provided by the dc-dc module or other device (load).
4
GND
Tie this pin directly to the system's analog GND plane
5
TIMER
Current Limit Response Timer: A capacitor connected from this pin to GND provides
overcurrent filtering to prevent nuisance "tripping" of the circuit breaker by setting the time
(t
FLT
) for which the controller is allowed to remain in current limit. Once the MIC2587 circuit
breaker trips, the output latches off. Under normal (steady state) operation, the TIMER pin
is held to GND by an internal 3.5
A current source (I
TIMERDN
). When the voltage across the
external sense resistor exceeds the V
TRIP
threshold, an internal 65
A current source
(I
TIMERUP
) is activated to charge the capacitor connected to the TIMER pin. When the TIMER
pin voltage reaches the V
TIMERH
threshold, the circuit breaker is tripped pulling the GATE pin
low, the I
TIMERUP
current source is disabled, and the TIMER pin capacitor is discharged by
the I
TIMERDN
current source. When the voltage at the TIMER pin is less than 0.5V, the
MIC2587 can be restarted by toggling the ON pin LOW then HIGH.
For the MIC2587R, the capacitor connected to the TIMER pin sets the period of auto-retry
where the duty cycle is fixed at a nominal 5%.
Micrel
MIC2587/MIC2587R
October 2004
4
M9999-102204
(408) 955-1690
Pin Description
Pin Number
Pin Name
Pin Function
6 GATE
Gate Drive Output: This pin is the output of an internal charge pump connected to the gate
of an external, N-channel power MOSFET. The charge pump has been designed to provide
a minimum gate drive (
V
GATE
= V
GATE
- V
CC
) of +7.5V over the input supply's full operating
range. When the ON pin voltage is higher than the V
ONH
threshold, a 16
A current source
(I
GATEON
) charges the GATE pin.
When in current limit, the output voltage at the GATE pin is adjusted so that the voltage
across the external sense resistor is held equal to V
TRIP
while the capacitor connected to the
TIMER pin charges. If the current limit condition goes away before the TIMER pin voltage
rises above the V
TIMERH
threshold, then steady-state operation resumes.
The GATE output pin is shut down whenever: (1) the input supply voltage is lower than the
V
UVL
threshold, (2) the ON pin voltage is lower than the V
ONL
threshold, (3) the TIMER pin
voltage is higher than the V
TIMERH
threshold, or (4) the difference between the VCC and
SENSE pins is greater than V
TRIP
while the TIMER pin is grounded. For cases (3) and (4)
overcurrent fault conditions the GATE is immediately pulled to ground by I
GATEFLT
, a 30mA
(minimum) pull-down current.
7 SENSE
Circuit Breaker Sense Input: This pin is the (-) Kelvin sense connection for the output
supply rail. A low-valued resistor (R
SENSE
) between this pin and the VCC pin sets the circuit
breaker's current limit trip point. When the current limit detector circuit is enabled (as well as
the current limit timer), while the FB pin voltage remains higher than 1V, the voltage across
the sense resistor (V
CC
-V
SENSE
) will be regulated to V
TRIP
(47mV, typically) to maintain a
constant current into the load. When the FB pin voltage is less than
0.5V, the voltage
across the sense resistor decreases linearly to a minimum of 12mV (typical) when the FB
pin voltage is at 0V.
To disable the circuit breaker (and defeat all current limit protections), the SENSE pin and
the VCC pin can be tied together.
8 VCC
Positive Supply Voltage Input: This pin is the (+) Kelvin sense connection for the output
supply rail. The nominal operating voltage range for the MIC2587 and the MIC2587R is
+10V to +80V, and VCC can withstand input transients up to +100V. An undervoltage
lockout circuit holds the GATE pin low whenever the supply voltage to the MIC2587 and the
MIC2587R is less than the V
UVH
threshold.
Micrel
MIC2587/MIC2587R
October 2004
5
M9999-102204
(408) 955-1690
Absolute Maximum Ratings
(1)
(All voltages are referred to GND)
Supply Voltage (V
CC
) pin .............................. -0.3V to +100V
GATE pin...................................................... -0.3V to +100V
ON, SENSE pins .......................................... -0.3V to +100V
PWRGD, /PWRGD pins............................... -0.3V to +100V
FB pin........................................................... -0.3V to +100V
TIMER pin ........................................................ -0.3V to +6V
ESD Rating
Human
Body
Model ................................................. 2kV
Machine Model ......................................................200V
Lead Temperature (Soldering)
Standard Package (-xBM)
IR Reflow..............................240
C + 0
C/-5
C
Lead-Free Package (-xYM)
IR Reflow..............................260
C + 0
C/-5
C
Operating Ratings
(2)
Supply Voltage (V
CC
)...................................... +10V to +80V
Ambient Temperature Range (T
A
) ............... -40
C to +85
C
Junction Temperature (T
J
) ....................................... +125
C
Package Thermal Resistance (
JA
)
8-pin
SOIC...................................................... 160
C/W
DC Electrical Characteristics
(4)
V
CC
= +24V and +48V, T
A
= 25
C, unless otherwise noted. BOLD indicates specifications apply over the full operating temperature
range of -40
C to +85
C.
Symbol Parameter
Condition
Min
Typ
Max
Units
V
CC
Supply Voltage
10
80
V
I
CC
Supply Current
2
5
mA
V
UVH
V
UVL
Supply Voltage Undervoltage Lockout
V
CC
rising
V
CC
falling
7.5
7.0
8.0
7.5
8.5
8.0
V
V
V
HYSLO
VCC Undervoltage Lockout Hysteresis
500
mV
V
FBH
Feedback Pin Voltage High Threshold
FB Low-to-High transition
1.280
1.313
1.345
V
V
FBL
Feedback Pin Voltage Low Threshold
FB High-to-Low transition
1.208
1.233
1.258
V
V
HYSFB
Feedback Voltage Hysteresis
80
mV
V
FB
FB Pin Threshold Line Regulation
10V
V
CC
80V
-0.05
0.05
mV/V
I
FB
FB Pin Input Current
0V
V
FB
3V
-1
1
A
V
TRIP
Circuit Breaker Trip Voltage, V
CC
-V
SENSE
V
FB
= 0V (See Fig. 1)
V
FB
= 1V (See Fig. 1)
5
39
12
47
17
55
mV
mV
V
GATE
MOSFET Gate Drive, V
GATE
-V
CC
+10V
V
CC
+80V
7.5
18
V
I
GATEON
GATE Pin Pull-up Current
Start cycle, V
GATE
= 7V
-10
-16
-22
A
I
GATEFLT
GATE Pin rapid pull-down current (during
a fault condition, until V
GATE
= V
GATE[TH]
)
(V
GATE[TH]
is the MOSFET threshold)
(V
CC
- V
SENSE
) = (V
TRIP
+ 10mV)
V
GATE
= 5V
30
80
200
mA
I
GATEOFF
GATE Pin Turn-off Current
Normal turn-off, or from V
GATE[TH]
(MOSFET) to 0V after a fault condition
1.8
mA
I
TIMERUP
TIMER Pin Charging Current
(V
CC
V
SENSE
) > V
TRIP
V
TIMER
= 0V
-24
-65
-120
A
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