MIC2589 [MICREL]
SINGLE-CHANNEL NEGATIVE HIGH VOLTAGE HOT SWAP POWER CONTROLLERS/SEQUENCERS; 单通道负高压热插拔电源控制器/音序器
| 型号： | MIC2589 |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | SINGLE-CHANNEL NEGATIVE HIGH VOLTAGE HOT SWAP POWER CONTROLLERS/SEQUENCERS |
| 文件： | 总17页 (文件大小：101K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC2589/MIC2595
Single-Channel, Negative High-Voltage Hot
Swap Power Controllers/Sequencers
General Description
Features
The MIC2589 and MIC2595 are single-channel, negative-
voltagehotswapcontrollersdesignedtoaddresstheneedfor
safe insertion and removal of circuit boards into “live” system
backplanes, while using few external components. The
MIC2589/89R and the MIC2595/95R are each available in
14-pin SOIC packaging and work in conjunction with an
external N-Channel MOSFET for which the gate drive is
controlled to provide inrush current limiting and output volt-
age slew-rate control. Overcurrent fault protection is also
provided for which the overcurrent threshold and the
overcurrent duration are programmable. Very fast fault re-
sponse is provided to ensure that system power supplies
maintain regulation even during output short circuits. This
familyofferstworesponsestoacircuitbreakerfaultcondition:
the MIC2589 and MIC2595 latch the circuit breaker’s output
off if the overcurrent threshold interval is exceeded while the
MIC2589R and MIC2595R automatically attempt to restart at
a fixed duty cycle after a current limit fault. A primary
Power-Good signal and two secondary (delayed and stag-
gered) Power-Good signals are provided to indicate that the
output voltage of the inrush current limiter is within its valid
operatingrange. Thesesignalscanbeusedtoperformanall-
at-once or a sequenced enabling of one or more DC-DC
power modules.
• Provides safe insertion and removal from live
–48V (nominal) backplanes
• Operates from –19V to –80V
• Fast responding circuit breaker (<1µs) to short circuit
conditions
• User-programmable overcurrent detector response time
• Electronic circuit breaker function:
Output latch OFF (MIC2589/95) or
Output auto-retry (MIC2589R/95R)
• Active current regulation precisely controls inrush
currents
• Regulated maximum output currents into faults
• Programmable undervoltage and overvoltage lockouts
(MIC2589/89R)
• Programmable UVLO hysteresis (MIC2595/95R)
• Staggered ‘Power-Good’ outputs provide load
sequencing
• Fault reporting:
Active-HIGH (MIC25XX-1) and Active-LOW
(MIC25XX-2) Power-Good signal output
Applications
• Central office switching
• –48V power distribution
• Distributed power systems
All support documentation can be found on Micrel’s web
site at www.micrel.com.
Typical Application
DC-DC Converter
–
48V
RETURN
+2.5V
IN+
OUT
(Long Pin)
100µF
/ON/OFF
MIC2589-1BM
MIC2589R-1BM
–
48V
+2.5V
IN–
GND
RETURN
RETURN
1
(Short Pin)
14
3
PWRGD1
PWRGD2
PWRGD3
PGTIMER
CFILTER
CNLD
VDD
UV
R1
698kΩ
1%
12
13
DC-DC Converter
IN+ OUT
+3.3V
2
5
6
R2
11.8kΩ
1%
100µF
/ON/OFF
+3.3V
RETURN
4
IN–
GND
OV
R3
12.4kΩ
1%
VEE
SENSE GATE DRAIN
7
9
10
11
CFILTER
CPG
DC-DC Converter
IN+ OUT
CNLD
R4
0Ω
CGATE
+5V
100µF
M1
/ON/OFF
–
48V
+5V
RETURN
IN–
GND
INPUT
(Long Pin)
RSENSE
Input Overvoltage = 71.2V
Input Undervoltage = 36.5V
(See "Functional Description"ˇ for more detail)
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
M9999-031504
March 2004
1
MIC2589/2595
Micrel
Ordering Information
PWRGD
Polarity
Circuit Breaker
Function
Part Number
Input Voltage Monitor Pins
Programmable UVLO & OVLO
Programmable UVLO & OVLO
Programmable UVLO & OVLO
Programmable UVLO & OVLO
Programmable UVLO Hysteresis
Programmable UVLO Hysteresis
Programmable UVLO Hysteresis
Programmable UVLO Hysteresis
Package
MIC2589-1BM
MIC2589-2BM
MIC2589R-1BM
MIC2589R-2BM
MIC2595-1BM
MIC2595-2BM
MIC2595R-1BM
MIC2595R-2BM
Active-High
Active-Low
Active-High
Active-Low
Active-High
Active-Low
Active-High
Active-Low
Latched Off
Latched Off
Auto-Retry
Auto-Retry
Latched Off
Latched Off
Auto-Retry
Auto-Retry
14-pin SOIC
14-pin SOIC
14-pin SOIC
14-pin SOIC
14-pin SOIC
14-pin SOIC
14 pin SOIC
14-pin SOIC
Pin Configuration
PWRGD1
PGTIMER
UV
1
2
3
4
5
6
7
14 VDD
/PWRGD1
1
2
3
4
5
6
7
14 VDD
13 PWRGD3
12 PWRGD2
11 DRAIN
PGTIMER
UV
13 /PWRGD3
12 /PWRGD2
11 DRAIN
10 GATE
OV
OV
CFILTER
CNLD
VEE
10 GATE
CFILTER
CNLD
VEE
9
8
SENSE
NC
9
8
SENSE
NC
14-Pin SOIC (M)
MIC2589-1BM
MIC2589R-1BM
14-Pin SOIC (M)
MIC2589-2BM
MIC2589R-2BM
PWRGD1
PGTIMER
OFF
1
2
3
4
5
6
7
14 VDD
/PWRGD1
PGTIMER
OFF
1
2
3
4
5
6
7
14 VDD
13 PWRGD3
12 PWRGD2
11 DRAIN
10 GATE
13 /PWRGD3
12 /PWRGD2
11 DRAIN
10 GATE
ON
ON
CFILTER
CNLD
CFILTER
CNLD
9
8
SENSE
NC
9
8
SENSE
NC
VEE
VEE
14-Pin SOIC (M)
MIC2595-1BM
MIC2595R-1BM
14-Pin SOIC (M)
MIC2595-2BM
MIC2595R-2BM
M9999-031504
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March 2004
MIC2589/2595
Pin Description
Pin Number
Micrel
Pin Name
Pin Function
PWRGD1
(MIC25XX-1)
Active-High
Power-Good Output 1: Asserted when the voltage on the DRAIN pin
(VDRAIN) is within VPGTH of VEE, indicating that the output voltage is within
proper specifications. For the MIC2589-1 and MIC2985-1, PWRGD1 will be
high impedance when VDRAIN is less than VPGTH, and will pull-down to
VDRAIN when VDRAIN is greater than VPGTH. For the MIC2589-2 and
MIC2595-2, /PWRGD1 will pull-down to VDRAIN when VDRAIN is less than
1
2
3
/PWRGD1
(MIC25XX-2)
Active-Low
VPGTH, and will be high-impedance when VDRAIN is greater than VPGTH
.
PGTIMER
A capacitor connected from this pin to VEE sets the time interval between
assertions of PWRGD2 (or /PWRGD2) and PWRGD3 (or /PWRGD3)
relative to PWRGD1 (or /PWRGD1). See the “Functional Description” for
further detail.
UV
Threshold
MIC2589 and MIC2589R: Undervoltage Threshold Input. When the voltage
at the UV pin is less than the VUVL threshold, the GATE pin is immediately
pulled low by an internal 100µA current pull-down. The UV pin is also used
to cycle the device off and on to reset the circuit breaker. Taken together,
the OV and UV pins form a window comparator which define the limits of
VEE within which the load may safely be powered.
3
OFF
MIC2595 and MIC2595R: Turn-Off Threshold. When the voltage at the OFF
pin is less than the VOFFL threshold, the GATE pin is immediately pulled
low by an internal 100µA current pull-down. The OFF pin is also used to cycle
the device off and on to reset the circuit breaker. Taken together, the ON
and OFF pins provide programmable hysteresis for the MIC2595 to be
enabled.
(Turn-Off Threshold)
4
4
5
OV
Threshold
MIC2589 and MIC2589R: Overvoltage Threshold Input. When the voltage
at the OV pin is greater than the VOVH threshold, the GATE pin is immediately
pulled low by an internal 100µA current pull-down.
ON
MIC2595 and MIC2595R: Turn-On Threshold. At initial system power-up or
after the part has been shut off by the OFF pin, the voltage on the ON pin
must be above the VONH threshold in order for the MIC2595 to be enabled.
(Turn-On Threshold)
CFILTER
Current Limit Response Timer: A capacitor connected between this pin and
VEE provides filtering against nuisance tripping of the circuit breaker by
setting a time delay, tFLT, for which an overcurrent event must last prior to
signaling a fault condition and latching the output off. The minimum time for
tFLT will be the time it takes for the output (capacitance) to charge to VEE
during start-up. This pin is held to VEE with a 3µA current pull-down when
no current limit condition exists. See the “Functional Description” for further
details.
6
CNLD
No-Load Detect Timer: A capacitor between this pin and VEE sets the
interval, tNLD, for which the current through the external MOSFET can drop
below 10% of full-scale current limit before the circuit breaker is tripped.
Tying this pin to VEE will disable this function. This pin is held to VEE by an
internal NMOS when there is no undercurrent condition.
7
8
9
VEE
NC
Negative Supply Voltage Input.
No Internal Connection.
SENSE
Circuit Breaker Sense Input: A resistor between this pin and VEE sets the
current limit trip point for the circuit. When the current limit threshold of IR =
50mV is exceeded for tFLT, the circuit breaker is tripped and the GATE pin is
immediately pulled low. Toggling UV or OV will reset the circuit breaker. To
disable the circuit breaker, externally tie SENSE and VEE can be connected
together.
10
11
GATE
Gate Drive Output: Connects to the Gate of an N-Channel MOSFET.
Drain Sense Input: Connects to the Drain of an N-Channel MOSFET.
DRAIN
March 2004
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M9999-031504
MIC2589/2595
Micrel
Pin Number
Pin Name
Pin Function
12
PWRGD2
(MIC2589-1)
(MIC2595-1)
Power-Good Output 2: Asserted when the following is true: (PWRGD1 =
Asserted) AND (Time after Assertion of PWRGD1 = Time PWRGD2, as
programmed by the capacitor on PGTIMER). Once PWRGD1 is asserted,
the PGTIMER pin begins to change and PWRGD2 will assert when
PGTIMER crosses the PWRGD2 threshold (VTHRESH(PG2) = 0.63V, typical).
Also see PWRGD1 and PGTIMER pin descriptions.
12
13
13
14
/PWRGD2
(MIC2589-2)
(MIC2595-2)
/Power-Good Output 2: Asserted when the following is true: (/PWRGD1 =
Asserted) AND (Time after Assertion of /PWRGD1 = Time /PWRGD2, as
programmed by the capacitor on PGTIMER). Once /PWRGD1 is asserted, the
PGTIMER pin begins to change and /PWRGD2 will assert when PGTIMER
crosses the /PWRGD2 threshold (VTHRESH(PG2) = 0.63V, typical). Also see
/PWRGD1 and PGTIMER pin descriptions.
PWRGD3
(MIC2589-1)
(MIC2595-1)
Power-Good Output 3: Asserted when the following is true: (PWRGD1 =
Asserted) AND (Time after Assertion of PWRGD1 = Time PWRGD3, as
programmed by the capacitor on PGTIMER). Once PWRGD1 is asserted,
the PGTIMER pin begins to change and PWRGD3 will assert when
PGTIMER crosses the PWRGD3 threshold (VTHRESH(PG3) = 1.15V, typical).
Also see PWRGD1 and PGTIMER pin descriptions.
/PWRGD3
(MIC2589-2)
(MIC2595-2)
/Power-Good Output 3: Open Collector. Asserted when the following is true:
(/PWRGD1 = Asserted) AND (Time after Assertion of /PWRGD1 = Time
/PWRGD3, as programmed by the capacitor on PGTIMER). Once /PWRGD1
is asserted, the PGTIMER pin begins to change and /PWRGD3 will assert
when PGTIMER crosses the /PWRGD3 threshold (VTHRESH(PG3) = 1.15V,
typical). Also see /PWRGD1 and PGTIMER pin descriptions.
VDD
Positive Supply Input.
M9999-031504
4
March 2004
MIC2589/2595
Micrel
Absolute Maximum Ratings(1)
Operating Ratings(2)
(All voltages are referred to V
)
Supply Voltage (V -V )............................. +19V to +80V
EE
DD EE
Ambient Temperature Range (T ) ............... –40°C to 85°C
Supply Voltage (V – V ) ......................... –0.3V to 100V
A
DD
EE
Junction Temperature (T ) ........................................ 125°C
DRAIN, PWRGD pins................................... –0.3V to 100V
GATE pin..................................................... –0.3V to 12.5V
SENSE, OV, UV, ON, OFF pins....................... –0.3V to 6V
J
Package Thermal Resistance
SOIC (θ ) .........................................................120°C/W
JA
(3)
ESD Ratings .............................................................................. 2kV
Soldering
Vapor Phase .......................... (60 sec.) +220°C +5 ±0°C
Infrared ................................... (15 sec.) +235°C +5 ±0°C
DC Electrical Characteristics(4)
VDD = 48V, VEE = 0V, TA = 25°C, unless otherwise noted. Bold indicates specifications apply over the full operating temperature range of –40°C to 85°C.
Symbol
VDD – VEE
IDD
Parameter
Condition
Min
19
Typ
Max
80
6
Units
Supply Voltage
Supply Current
4
mA
mV
VTRIP
Circuit Breaker Trip Voltage
No-Load Detect Threshold
VTRIP = VSENSE – VEE
40
50
60
INLDTH
% of full-scale current limit
IOUT decreasing
IOUT increasing
20
22
%
%
INLDHYS
VCNLD
No-Load Detect Threshold Hysteresis % of full-scale current limit
2
%
V
No-Load Detect Timer High Threshold
Voltage
1.17
10
9
1.24
1.33
40
ICNLD
No-Load Detect Timer Capacitor
Charge Current
Note 5
25
10
45
µA
V
VGATE
IGATEON
GATE Drive Voltage, (VGATE – VEE
)
15V ≤ (VDD – VEE) ≤ 80V
11
GATE Pin Pull-Up Current
VGATE = VEE to 8V
30
60
µA
19V ≤ (VDD – VEE) ≤ 80V
ISENSE
SENSE Pin Current
VSENSE = 50mV
0.2
µA
IGATEOFF
GATE Pin Sink Current
(VSENSE – VEE) = 100mV
VGATE = 2V
100
240
mA
ICFILTER
CFILTER Charge Current
(VSENSE – VEE) > VTRIP
VCFILTER = 0.75V
VGATE = 3V
65
95
4
135
6
µA
µA
CFILTER Pull-Down Current
(VSENSE – VEE) < VTRIP
VCFILTER = 0.75V
VGATE = 3V
2
VCFILTER(TRIP) High Threshold Voltage
Overcurrent Detect Timer
(VSENSE – VEE) > VTRIP
1.17
0.17
30
1.25
0.22
45
1.33
0.25
80
V
V
VCFILTER(RETRY) Voltage on CFILTER to Trigger Auto-Retry
(MIC2589R and MIC2595R only)
IPGTIMER
PGTIMER Charge Current
Voltage on PGTIMER = 0.75 V
µA
Notes:
1. Exceeding the “Absolute Maximum Ratings” may damage the devices.
2. The devices are not guaranteed to function outside the specified Operating Conditions.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model: 1.5kΩ in series with 100pF. Machine model: 200pF, no series
resistance.
4. Specification for packaged product only.
5. Not 100% tested. Parameters are guaranteed by design.
March 2004
5
M9999-031504
MIC2589/2595
Micrel
DC Electrical Characteristics(6)
V
= 48V, V = 0V, T = 25°C, unless otherwise noted. Bold indicates specifications apply over the full operating temperature range of –40°C to 85°C.
DD
EE
A
Symbol
Parameter
Condition
Min
0.5
Typ
Max
0.8
Units
VTHRESH(PG2) PGTIMER Threshold Voltage for
PWRGD2 and /PWRGD2
0.63
V
VTHRESH(PG3) PGTIMER Threshold Voltage for
PWRGD3 and /PWRGD3
1.00
1.15
1.30
V
RPGTIMER
VOVH
PGTIMER Discharge Resistance
Voltage on PGTIMER = 0.5 V
Low-to-High transition
250
500
750
Ω
OV Pin High Threshold Voltage
(MIC2589 and 2589R parts only)
1.198
1.223
1.247
V
VOVL
OV Pin Low threshold Voltage
(MIC2589 and 2589R only)
High-to-Low transition
1.165
1.203
20
1.232
V
mV
V
VOVHYS
VUVL
OV Pin Hysteresis
(MIC2589 and 2589R only)
UV Pin Low threshold Voltage
(MIC2589 and 2589R only)
High-to-Low transition
Low-to-High transition
1.198
1.213
1.223
1.243
20
1.247
1.272
VUVH
UV Pin High Threshold Voltage
(MIC2589 and 2589R only)
V
VUVHYS
VONH
UV Pin Hysteresis
(MIC2589 and 2589R only)
mV
V
ON Pin High Threshold Voltage
(MIC2595 and 2595R only)
Low-to-High transition
High-to-Low transition
1.198
1.198
1.223
1.223
1.247
1.247
VOFFL
OFF Pin Low Threshold Voltage
(MIC2595 and 2595R only)
V
ICNTRL
VPGTH
Input Current (OV, UV, ON, OFF Pins)
Power-Good Threshold
VUV = 1.25V
0.5
µA
High-to-Low Transition
(VDRAIN – VEE
1.1
1.26
1.40
V
)
VOLPG
PWRGD Output Voltage
(relative to voltage at the DRAIN pin) 0mA ≤ IPG(LOW) ≤ 1mA
VOLPG – VDRAIN
MIC25XX-1
(VDRAIN – VEE) > VPGTH
(VDRAIN – VEE) < VPGTH
VPWRGD = VDD = 80 V
–0.25
–0.25
0
0.8
0.8
1
V
V
MIC25XX-2
ILKG(PG)
PWRGD Output Leakage Current
µA
Note:
6. Specification for packaged product only.
M9999-031504
6
March 2004
MIC2589/2595
Micrel
AC Electrical Characteristics(7)
Symbol
Parameter
Condition
Min
Typ
Max
Units
tOCSENSE
Overcurrent Sense to GATE Low
Trip Time, Figure 2
VSENSE – VEE = 100mV(8)
3.5
µs
tOVPHL
tOVPLH
tUVPHL
tUVPLH
tOFFPHL
tONPLH
tPGLH1
tPGHL1
tPGHL2
tPGLH2
OV High to GATE Low, Figure 3
(MIC2589 and 2589R only)
OV = 1.5V(8)
OV = 1.0V(8)
UV = 1.0V(8)
UV = 1.5V(8)
OFF = 1.0V(8)
ON = 1.5V(8)
1
1
1
1
1
1
3
5
5
3
µs
µs
µs
µs
µs
µs
µs
µs
µs
µs
OV Low to GATE High, Figure 3
(MIC2589 and 2589R only)
UV Low to GATE Low, Figure 4
(MIC2589 and 2589R only)
UV High to GATE High, Figure 4
(MIC2589 and 2589R only)
OFF Low to GATE Low, Figure 5
(MIC2595 and 2595R only)
ON High to GATE High, Figure 5
(MIC2595 and 2595R only)
DRAIN Low to PWRGD1 Output High
(-1)
CLOAD on PWRGDx = 50pF,
RPULLUP = 100kΩ(8)
DRAIN High to all PWRGDx Outputs
Low (-1)
CLOAD on PWRGDx = 50pF,
RPULLUP = 100kΩ(8)
DRAIN Low to /PWRGD1 Output Low
(-2)
CLOAD on /PWRGDx = 50pF,
RPULLUP = 100kΩ(8)
DRAIN High to all /PWRGDx Outputs
High (-2)
CLOAD on /PWRGDx = 50pF,
RPULLUP = 100kΩ(8)
Notes:
7. Specification for packaged product only.
8. Not 100% production tested. Parameters are guaranteed by design.
Test Circuit
[Section under construction]
March 2004
7
M9999-031504
MIC2589/2595
Micrel
Timing Diagrams
OVERCURRENT
EVENT
t < tFLT
t ≥ tFLT
ILIMIT
ILOAD
tNLD
INLDTH
0A
Output OFF
(at VDD
Load current is regulated
at ILIMIT = 50mV/RSENSE
)
VDRAIN
(at VEE
)
(at VEE
)
(at VEE)
VUV or VOFF
VUVL
V
UVH —
Reduction in VDRAIN to support
ILIMIT = 50mV/RSENSE
(VUV
—
VEE)
(VUV VEE
)
(at VEE
)
Figure 1. Overcurrent and Undercurrent (No Load) Response
100mV
VSENSE - VEE
tOCSENSE
VGATE
1V
Figure 2. SENSE to GATE LOW Timing Response
1.223V
1.203V
VOV
tOVPHL
tOVPLH
VGATE
1V
1V
Figure 3. MIC2589/89R Overvoltage Response
M9999-031504
8
March 2004
MIC2589/2595
Micrel
VUV
1.223V
1.243V
tUVPHL
tUVPLH
VGATE
1V
1V
Figure 4. MIC2589/89R Undervoltage Response
VOFF
1.223V
tOFFHL
VGATE
1V
Figure 5a. MIC2595/95R OFF to GATE Drive Response
1.223V
VON
tONLH
VGATE
1V
Figure 5b. MIC2595/95R ON to GATE Drive Response
MIC2589/95-1
VDRAIN
VPGTH
VPGTH
VEE
tPGLH1
tPGHL1
PWRGDx not asserted
VPWRGD — VDRAIN = 0V
PWRGDx asserted - High Impedance
PWRGDx not asserted
VPWRGD — VDRAIN = 0V
PWRGD
Outputs
VEE
PWRGD3
PWRGD1
PWRGD2
MIC2589/95-2
VDRAIN
VPGTH
VPGTH
tPGLH2
VEE
tPGHL2
/PWRGD
Outputs
VEE
/PWRGD1
/PWRGD2
/PWRGD3
Figure 6. DRAIN to Power-Good Response
March 2004
9
M9999-031504
MIC2589/2595
Micrel
Functional Diagram
VDD1
Internal VDD
and
Reference
Generator
VDD1
VREF
VDD
45µA
GATE
Error
AMP
+
SENSE
–
100µA
VEE
VEE
50mV
VEE
VDD1
VDD1
PWRGD1
PWRGD2
PWRGD3
95µA
+
CFILTER
VCFILTER
–
VEE
4µA
VREF
/PWRGD1
/PWRGD2
/PWRGD3
VEE
Logic +
Circuit
Breaker
EN
VDD1
25µA
VEE
6V
+
CNLD
–
DRAIN
Clamp
VCNLD
–
+
VPGTH
Internal
PG
VDD1
45µA
VEE
UV
–
PGTIMER
+
+
–
VTH(PG2)
VTH(UV/OV)
+
–
–
+
VTH(PG3)
OV
VEE
For Power-Good circuitry only
denotes -2 option
MIC2589 Block Diagram
M9999-031504
10
March 2004
MIC2589/2595
Micrel
The Power-Good Output Signals
Functional Description
Hot Swap Insertion
For the MIC2589/95-1 and MIC2589R/95R-1, power-good
output signal PWRGD1 will be high impedance when V
DRAIN
When circuit boards are inserted into systems carrying live
supply voltages (“hot swapped”), high inrush currents often
result due to the charging of bulk capacitance that resides
across the circuit board’s supply pins. These current spikes
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 swap
event may cause permanent damage to connectors or on-
board components.
drops below V
, and will pull-down to V
when
PGTH
DRAIN
V
is above V
. For the MIC2589/95-2 and the
DRAIN
PGTH
MIC2589R/95R-2, power-good output signal /PWRGD1 will
pull down to the potential of the V
pin when V
DRAIN
DRAIN
and will be high impedance when V
DRAIN
drops below V
is above V
PGTH
. Hence, the -1 parts have an active-high
PGTH
PWRGD signalandthe-2partshaveanactive-low/PWRGD
X
X
output. PWRGD (or /PWRGD ) may be used as an enable
X
X
signal for one or more following DC/DC converter modules or
for other system uses as desired. When used as an enable
signal, the time necessary for the PWRGD (or /PWRGD)
signal to pull-up (when in high impedance state) will depend
upon the load (RC) that is present on this output.
The MIC2589 and the MIC2595 are designed to address
these issues by limiting the maximum current, which is
allowed to flow during hot swap events. This is achieved by
implementing a constant-current loop at turn-on. In addition
to inrush current control, the MIC2589 and the MIC2595
incorporate input voltage supervisory functions and user-
programmable overcurrent protection, thereby providing ro-
bust protection for both the system and the circuit board.
Power-good output signals PWRGD2 (/PWRGD2) and
PWRGD3 (/PWRGD3) follow the assertion of PWRGD1
(/PWRGD1) with a sequencing delay set by an external
capacitor (C ) from the controller’s PGTIMER pin (Pin 2) to
PG
Start-Up Cycle
V
. An expression for the sequencing delay between
EE
PWRGD2 and PWRGD1 is given by:
WhentheinputvoltageistotheICisbetweentheovervoltage
and undervoltage thresholds (MIC2589 and MIC2589R) or is
V
THRESH(PG2) × CPG
greater than V (MIC2595 and MIC2595R), a start cycle is
tPGDLY2−1
where V
=
ON
IPGTIMER
initiated. When the IC is enabled, the GATE pin voltage rises
from 0V with respect to V to approximately 10V above V
.
EE
EE
(= 0.63V, typically) is the PWRGD2
THRESH(PG2)
This 10V gate drive is sufficient to fully enhance commonly
availablepowerMOSFETsforthelowestpossibleDClosses.
threshold voltage for PGTIMER and I
(= 45µA, typi-
PGTIMER
cally) is the internal PGTIMER charge current. Similarly, an
expression for the sequencing delay between PWRGD3 and
PWRGD2 is given by:
Capacitor C
compensates circuitry internal to the IC,
GATE
while R4 minimizes the potential for high frequency parasitic
oscillations from occurring in M1. The drain current of the
MOSFET is regulated to ensure that it never exceeds the
programmed threshold, as described in the “Circuit Breaker
Function” section.
V
– V
× C
PG
(
)
THRESH(PG3)
THRESH(PG2)
t
=
PGDLY3−2
I
PGTIMER
Capacitor C
sets the value of overcurrent detector
where V
(= 1.15V, typically) is the PWRGD3
FILTER
THRESH(PG3)
delay, t , which is the time for which an overcurrent event
threshold voltage for PGTIMER. Therefore, power-good out-
put signal PWRGD2 (/PWRGD2) will be delayed after the
assertion of PWRGD1 (/PWRGD1) by:
FLT
must last to signal a fault condition and to cause an output
latch-off. These devices will be driving a capacitive load in
most applications, so a properly chosen value of C
prevents false-, or nuisance-, tripping at turn-on as well as
providing immunity to noise spikes after the start-up cycle is
complete. The procedure for selecting a value for C
FILTER
t
(ms) 14 × C (µF) ms
PG
PGDLY2-1
Power-good output signal PWRGD3 (/PWRGD3) follows the
assertion of PWRGD2 by a delay:
is
FILTER
t
(ms) 11.5 × C (µF) ms
PG
given in the “Circuit Breaker Function” section.
PGDLY3-2
For example, for a 10µF value for C , power-good output
ResistorR4,inserieswiththepowerMOSFET’sgate,maybe
required in some layouts to minimize the potential for para-
siticoscillationsoccurringinM1. Notethough, thatresistance
in this device of the circuit has a slight destabilizing effect
upon the MIC2589/95’s current regulation loop. If possible,
usehigh-frequencyPCBlayouttechniquesanduseadummy
resistor, such that R4 = 0Ω. If during prototyping an R4 is
required, common values for R4 range between 4.7Ω to 20Ω
for various power MOSFETs.
PG
signal PWRGD2 will be asserted 140ms after PWRGD1.
Power-good signal PWRGD3 will then be asserted 140ms
after PWRGD2 and 255ms after the assertion of PWRGD1.
The relationships between V
, V
, PWRGD1,
DRAIN
PGTH
PWRGD2, and PWRGD3 are shown in Figure 6.
March 2004
11
M9999-031504
MIC2589/2595
Micrel
Circuit Breaker Function
For example, in a system with a C
= 150µF, a maximum
LOAD
(V –V )=72V, andamaximumloadcurrentonanominal
–48V buss of 1.65A, the nominal circuit design equations
steps are:
The MIC2589/89R and the MIC2595/95R employ an elec-
troniccircuitbreakerthatprotectstheexternalpowerMOSFET
and other system components against large-scale faults,
such as short circuits. The current-limit threshold is set via an
DD
EE
1. Choose I
= I
(nom) = 2A (1.65A + 20%);
LIMIT
HOT_SWAP
external resistor, R
, connected between the V and
SENSE
EE
38.8mV
2A
standard value is 19.6mΩ);
SENSE. For the MIC2589/89R and MIC2595/95R, a timer is
set via capacitor C that determines the length of the
R
=
= 19.4mΩ
(closest 1%
2. Select an
SENSE
FILTER
time delay (t ) for which the device remains in current limit
FLT
3. Using I = I = 2A, the application circuit turn-
before the circuit breaker is tripped. This programmable
delay prevents tripping of the circuit breaker because of high
inrush current charging bulk and distributed capacitive loads.
Whenever the voltage across R
things happen:
CHARGE
LIMIT
on time is calculated:
150µF × 72V
(
)
= 5.4ms (use 6 ms)
exceeds 50mV, two
tTURN-ON
=
SENSE
2A
Allowing for capacitor tolerances and a nominal 6ms turn-on
time, an initial worst-case value for C is:
1. A constant-current regulation loop is engaged which
isdesignedtoholdthevoltageacrossR equal
FILTER
–6
SENSE
to 50mV. This protects both the load and the
MIC2589/95circuitsfromexcessivelyhighcurrents.
This current-regulation loop will engage in less than
1µs from the time at which the overvoltage condition
C
= 6ms x (115.4 × 10 µF/sec) = 692nF
FILTER(WORST-CASE)
The closest standard ±5% tolerance capacitor value is 698nF
and would be a good initial starting value for prototyping.
Wheneverthehotswapcontrollerisnotincurrentlimit, C
FILTER
on R
occurs.
SENSE
is discharged to V by an internal 4µA current source.
EE
2. Capacitor C
is charged up to an internal
FILTER
For the MIC2589R/95R devices, the circuit breaker automati-
V
threshold (= 1.25V) by an internal
CFILTER(TRIP)
cally resets after (20) t
time constants (20 × t ). If the fault
FLT
FLT
95µA current source. If the voltage across C
FILTER
condition still exists, capacitor C
will again be charge up
FILTER
crosses this threshold, the circuit breaker trips and
theGATEpinisimmediatelypulledlowbyaninternal
current pull-down. This operation turns off the
MOSFETquicklyanddisconnectstheinputfromthe
to V
C
where the circuit breaker is tripped. Capacitor
will then be discharged by an internal 4µA current
FILTER(TRIP)
FILTER
source until the voltage across C
goes below
FILTER
V
, at which time another start cycle is initiated.
FILTER(RETRY)
load. The value of C
should be selected to
FILTER
This will continue until the fault condition is removed or input
power is removed/cycled. The duty cycle of the auto-restart
function is therefore fixed at 5% and the period of the auto-
restart cycle is given by:
allow the circuit’s minimum regulated value of I
OUT
to equal I
for somewhat longer than the time it
TRIP
takes to charge the total load capacitance.
An initial value for C is found by calculating the time it
FILTER
will take for the MIC2589/95 to completely charge up the
output capacitive load. Assuming the load is enabled by the
PWRGD (or/PWRGD )signal(s)oftheIC,theturn-ondelay
time is derived from the following expression,
I = C × (dv/dt):
C
× 1.25V – 0.22V
(
)
(
)
FILTER
t
= 20 ×
AUTO-RESTART
95µA
X
X
ms
= C
× 216.8
FILTER
µF
C
× V – V
EE
(
)
The auto-restart period for the example above where the
LOAD
DD
t
=
TURN-ON
worst-case C
t
was determined to be 698nF is:
= 151ms
I
FILTER
LIMIT
AUTO-RESTART
Using parametric values specific to the MIC2589/95, an
expression relating a design nominal value for C
Current Sensing
to the
FILTER
circuit’s turn-on delay time is:
Asmentionedbefore,theMIC2589/89RandtheMIC2595/95R
use an external, low-value resistor in series with the source
of the external MOSFET to measure the current flowing into
t
×I
(typ)
(
)
TURN-ON
CFILTER
C
(nom) =
FILTER
the load. The V connection (Pin 7) to the IC is one input to
V
(typ)
EE
CFILTER
the device’s internal current sensing circuits and the SENSE
connection (Pin 9) is the other input.
t
× 95µA
µF
TURN-ON
–6
=
= t
× 76 ×10
TURN-ON
1.25V
sec
The sense resistor is nominally valued at:
Substituting the variables above with the specification limits
oftheMIC2589/95,anexpressionfortheworst-casevaluefor
VTRIP(typ)
RSENSE(nom) =
C
is given by:
IHOT_SWAP(nom)
FILTER
135µA
where V
voltage (= 50mV) and I
(typ) is the nominal circuit breaker threshold
TRIP
C
(max) = t
×
TURN-ON
FILTER
(nom) is the nominal hot
1.17V
HOT_SWAP
swaploadcurrentleveltotriptheinternalcircuitbreakerinthe
application.
µF
–6
= t
× 115.4 ×10
TURN-ON
sec
M9999-031504
12
March 2004
MIC2589/2595
Micrel
Toaccommodateworst-casetolerancesinthesenseresistor
(for a ±1% initial tolerance, allow ±3% tolerance for variations
over time and temperature) and circuit breaker threshold
voltages, a slightly more detailed calculation must be used to
determine the minimum and maximum hot swap load cur-
rents.
current, the controller’s no-load detection loop is enabled. In
this loop, an internal current source, I
, will charge an
CNLD
external capacitor C
. An expression for the controller’s
NLD
no-load time-out delay is given by:
C
NLD
t
= V
×
NLD
CNLD
I
As the MIC2589/95’s minimum current-limit threshold volt-
age is 40mV, the minimum hot swap load current is deter-
mined where the sense resistor is 3% high:
CNLD
where V
= 1.24V (typ); I
= 25µA (typ); and C
is
CNLD
CNLD
NLD
an external capacitor connected from Pin 6 to V . Once the
EE
40mV
38.8mV
voltageonC
reachesitsno-loadthresholdvoltage,V
,
NLD
CNLD
IHOT_SWAP(min) =
=
the loop times out and the controller will shut down until it is
resetmanually(MIC2589/95)oruntilitperformsanauto-retry
operation (MIC2589R/95R).
1.03 ×RSENSE(nom) RSENSE(nom)
Keep in mind that the minimum hot swap load current should
be greater than the application circuit’s upper steady-state
load current boundary. Once the lower value of R
Undervoltage/Overvoltage Detection (MIC2589 and
MIC2589R)
has
SENSE
beencalculated, itisgoodpracticetocheckthemaximumhot
swaploadcurrent(I (max))whichthecircuitmaylet
The MIC2589 and the MIC2589R have “UV” and “OV” input
pins that can be used to detect input supply rail undervoltage
and overvoltage conditions. Undervoltage lockout prevents
energizing the load until the supply input is stable and within
tolerance. In a similar fashion, overvoltage turnoff prevents
damage to sensitive circuit components should the input
voltage exceed normal operational limits. Each of these pins
is internally connected to analog comparators with 20mV of
hysteresis. When the UV pin falls below its V
the OV pin is above its V
immediately pulled low. The GATE pin will be held low until
the UV pin is above its V threshold or the OV pin is below
HOT_SWAP
pass in the case of tolerance build-up in the opposite direc-
tion. Here, the worst-case maximum is found using a
V
(max) of 60mV and a sense resistor 3% low in value:
TRIP
60mV
0.97 ×R
61.9mV
R (nom)
SENSE
I
(max) =
=
HOT_SWAP
(nom)
SENSE
In this case, the application circuit must be sturdy enough to
operate over an ~1.6-to-1 range in hot swap load currents.
For example, if an MIC2595 circuit must pass a minimum hot
threshold or
UVL
threshold, the GATE pin is
OVH
swap load current of 4A without nuisance trips, R
SENSE
UVH
38.8mV
its V
threshold. The circuit’s UV and OV threshold voltage
OVL
= 9.7mΩ
should be set to
, and the nearest 1%
4A
standard value is 9.76mΩ. At the other tolerance extremes,
levels are programmed using the resistor divider R1, R2, and
R3asshowninthe“TypicalApplication”wheretheequations
to set the trip points are shown below. For the following
I
(max) for the circuit in question is then simply:
HOT_SWAP
example,thecircuit’sUVthresholdissettoV =37Vandthe
UV
61.9mV
I
(max) =
= 6.3A
OV threshold is set at V = 72V, values commonly used in
HOT_SWAP
OV
9.76mΩ
Central Office power distribution applications.
With a knowledge of the application circuit’s maximum hot
swap load current, the power dissipation rating of the sense
resistor can be determined using P = I × R. Here, The I is
R1+R2 +R3
(
)
V
= V
(typ)×
(typ)×
2
UV
UVL
R2 +R3
(
)
I
(max) = 6.3A and the R is R
(min) =
HOT_SWAP
SENSE
(0.97)(R
(nom)) = 9.47mΩ. Thus, the sense resistor’s
SENSE
R1+R2 +R3
(
)
maximum power dissipation is:
V
= V
OVH
OV
R3
2
P
= (6.3A) × (9.47mΩ) = 0.376W
MAX
Given V , V , and any one resistor value, the remaining
A 0.5Ω sense resistor is a good choice in this application.
UV
OV
two resistor values can be determined. A suggested value for
R3 is that which will provide approximately 100µA of current
throughthevoltagedividerchainatV =V .Thisyieldsthe
No-Load Detection
For those applications in which a minimum load current will
always be present, the no-load detect capability of the
MIC2589/89R/95/95R family offers system designer the abil-
ity to perform a shutdown operation on such fault conditions,
suchasanunscheduledorunexpectedremovalofPCboards
from the system or on-board fuse failure.
DD
UV
following as a starting point:
VOVH(typ)
1.223V
R3 =
=
= 12.23kΩ
100µA
100µA
The closest standard 1% value for R3 = 12.4kΩ. Solving for
R2 and R1 yields:
As long as the minimum current drawn by the load is at least
V
TRIP
20% of the maximum output current (defined by
),
R
SENSE
the output of the hot swap controllers will remain enabled. If
the output current falls below 12% of the maximum output
March 2004
13
M9999-031504
MIC2589/2595
Micrel
R1+R2 +R3
(
(typ)×
ONH
)
V
V
= V
OV
ON
R2 =R3 ×
–1
R3
V
UV
R1+R2 +R3
(
(typ)×
OFFL
)
V
= V
OFF
72V
37V
R2+R3
R2 = 12.4kΩ ×
–1 = 11.73kΩ
Given V
, V , and any one resistor value, the remaining
OFF ON
two resistor values can be readily determined. A suggested
value for R3 is that which will provide approximately 100µA of
The closest standard 1% values for R2 = 11.8kΩ. Lastly, the
value for R1 is calculated:
current through the voltage divider chain at V = V
. This
DD
OFF
yields the following as a starting point:
V
–1.223V
(
)
–R2
OV
R1=R3 ×
V
(typ)
1.223V
OFFL
1.223V
R3 =
=
= 12.23kΩ
100µA
100µA
The closest standard 1% value for R3 = 12.4kΩ. Solving for
R2 and R1 yields:
72V –1.223V
(
)
–R2
R1=12.4kΩ ×
R1= 705.81kΩ
1.223V
V
ON
R2 =R3 ×
–1
V
OFF
The closest standard 1% value for R1 = 698kΩ.
Using standard 1% resistor values, the circuit’s nominal
UV and OV thresholds are:
40V
R2 =12.4kΩ ×
–1 = 1.77kΩ
35V
V
V
= 36.5V
= 71.2V
UV
OV
The closest standard 1% value for R2 = 1.78 kΩ. Lastly, the
Programmable UVLO Hysteresis (MIC2595 and
MIC2595R)
value for R1 is calculated:
V
–1.223V
(
)
–R2
The MIC2595 and the MIC2595R devices have user-pro-
grammable hysteresis by means of the ON and OFF pins
(Pins 4 and 3, respectively). This allows setting the
MIC2595/95R to turn on at a voltage V1, and not turn off until
a second voltage V2, where V2 < V1. This can significantly
simplify dealing with source impedances in the supply buss
while at the same time increasing the amount of available
operating time from a loosely regulated power rail (for ex-
ample, a battery supply). The MIC2595/95R holds the output
ON
R1=R3 ×
1.223V
40V –1.223V
(
)
–R2
R1=12.4kΩ ×
1.223V
R1 = 391.38kΩ
The closest standard 1% value for R1 = 392kΩ.
Using standard 1% resistor values, the circuit’s nominal
ON and OFF thresholds are:
off until the voltage at the ON pin is above its V
threshold
ONH
value given in the “Electrical Characteristics” table. Once the
output has been enabled by the ON pin, it will remain on until
V
V
= 40.1V
= 35V
ON
OFF
the voltage at the OFF pin falls below its respective V
OFFL
threshold value, or the part turns off due to an external fault
condition. Should either event occur, the GATE pin is imme-
diately pulled low and will remain low until the ON pin voltage
once again above its V
threshold. The circuit’s turn-on
ONH
and turn-off voltage levels are set using the resistor divider
R1, R2, and R3 as shown in the “Typical Application” where
the equations to set the trip points are shown below. For the
following example, the circuit’s ON threshold is set to V
=
ON
40V and the circuit’s OFF threshold is set to
= 35V.
V
OFF
M9999-031504
14
March 2004
MIC2589/2595
Micrel
thiswilldamagethetransistor.However,theactual
Applications Information
4-Wire Kelvin Sensing
avalanche voltage is unknown; all that can be
guaranteed is that it will be greater than the V
BD(D-
Because of the low value typically required for the sense
resistor,specialcaremustbeusedtomeasureaccuratelythe
voltage drop across it. Specifically, the measurement tech-
of the MOSFET. The drain of the transistor is
S)
connected to the DRAIN pin of the MIC2589/95,
and the resulting transient does have enough
voltage and energy and can damage this, or any,
high-voltage hot swap controller.
nique across R
must employ 4-wire Kelvin sensing.
SENSE
This is simply a means of ensuring that any voltage drops in
the power traces connected to the resistors are not picked up
by the signal conductors measuring the voltages across the
sense resistors.
2. If the load’s bypass capacitance (for example, the
input filter capacitors for a set of DC-DC converter
modules) are on a board from which the board with
the MIC2589/95 and the MOSFET can be un-
plugged, thesametypeofinductivetransientdam-
age can occur to the MIC2589/95.
Figure 7 illustrates how to implement 4-wire Kelvin sensing.
Asthefigureshows,allthehighcurrentinthecircuit(fromV
EE
throughR
andthentothesourceoftheoutputMOSFET)
SENSE
flows directly through the power PCB traces and through
. The voltage drop across R is sampled in such
a way that the high currents through the power traces will not
introduce any parasitic voltage drops in the sense leads. It is
recommended to connect the hot swap controller’s sense
leads directly to the sense resistor’s metalized contact pads.
Protecting the controller and the power MOSFET from dam-
age against these large-scale transients can take the forms
shown in Figure 8. It is not mandatory that these techniques
are used - the application environment will dictate suitability.
As protection against sudden on-card load dumps at the
DRAIN pin of the controller, a 2.2µF or larger capacitor
directly from DRAIN to VEE of the controller can be used to
serve as a charge reservoir. Alternatively, a 68V, 1W, 5%
Zener diode clamp can be installed in a similar fashion. Note
thattheclampdiode’scathodeisconnectedtotheDRAINpin
as shown in Figure 8. To protect the hot swap controller from
large-scale transients at the card input, a 100V clamp diode
(an SMAT70A or equivalent) can be used. In either case, the
lead lengths should be short and the layout compact to
prevent unwanted transients in the protection circuit.
R
SENSE
SENSE
RSENSE metalized
contact pads
Power Trace
From VEE
Power Trace
To MOSFET Source
RSENSE
PCB Track Width:
0.03" per Ampere
using 1oz. Cu
Signal Trace
to MIC2589/95 VEE Pin
Signal Trace
to MIC2589/95 SENSE Pin
Note: Each SENSE lead trace shall be
balanced for best performance — equal
length/equal aspect ratio.
[Circuit drawing under construction]
Figure 7. 4-Wire Kelvin Sense Connections for R
Protection Against Voltage Transients
SENSE
Figure 8. Using Large-Scale Transient Protection
Devices Around the MIC2589/95 and the
MIC2589R/95R
In many telecom applications, it is very common for circuit
boards to encounter large-scale supply-voltage transients in
backplane environments. Because backplanes present a
compleximpedanceenvironment, thesetransientscanbeas
high as 2.5 times steady-state levels, or 120V in worst-case
situations. In addition, a sudden load dump anywhere on the
circuitcardcangenerateaveryhighvoltagespikeatthedrain
of the output MOSFET which, in turn, will appear at the
DRAIN pin of the MIC2589/95. In both cases, it is good
engineering practice to include protective measures to avoid
damaging sensitive ICs or the hot swap controller from these
large-scale transients. Two typical scenarios in which large-
scale transients occur are described below:
The same logic applies to the input of the MIC2589/95 circuit.
Power bus inductance could easily result in localized high-
voltage transients during a turn-off event. The potential for
overstressing the part in such a case should be kept in check
with a suitable input capacitor and/or transient clamping
diode.
Power MOSFET Selection
[Section under construction]
Power MOSFET Operating Voltage Requirements
[Section under construction]
1. Anoutputcurrentloaddumpwithnobypass(charge
bucket or bulk) capacitance to V . For example,
EE
Power MOSFET Steady-State Thermal Issues
if L
= 5µH, V = 56V and t
= 0.7µs, the
LOAD
IN
OFF
[Section under construction]
resulting peak short-circuit current prior to the
MOSFET turning off would reach:
55V × 0.7µs
(
)
= 7.7A
Power MOSFET Transient Thermal Issues
5µH
[Section under construction]
Ifthereisnootherpathforthiscurrenttotakewhen
the MOSFET turns off, it will avalanche the drain-
source junction of the MOSFET. Since the total
energy represented is small relative to the sturdi-
ness of modern power MOSFETs, it’s unlikely that
PCB Layout Considerations
[Section under construction]
March 2004
15
M9999-031504
MIC2589/2595
Micrel
Power MOSFET and Sense Resistor Vendors
Table 1 shows some of the various sense resistor types
available for use with the MIC2589/95 product family.
Resistor Vendors
Resistor Types
“WSL” Series
Contact Data
Vishay (Dale)
www.vishay.com/docs/wsl_30100.pdf
(203)452-5664
IRC
“OARS” Series
“LR” Series
(second source to “WSL”)
www.irctt.com/pdf_files/OARS.pdf
www.irctt.com/pdf_files/LRC.pdf
(828) 264-8861
Table 1. Suggested Sense Resistors
M9999-031504
16
March 2004
MIC2589/2595
Micrel
Package Information
PIN 1
DIMENSIONS:
INCHES (MM)
0.154 (3.90)
0.026 (0.65)
MAX)
0.193 (4.90)
0.050 (1.27) 0.016 (0.40)
TYP TYP
45°
0.006 (0.15)
3°–6°
0.244 (6.20)
0.228 (5.80)
0.344 (8.75)
0.337 (8.55)
SEATING
PLANE
0.057 (1.45)
0.049 (1.25)
14-Pin SOIC (M)
MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s
use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2004 Micrel, Incorporated.
March 2004
17
M9999-031504
相关型号：
MIC2589-1YM
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