SUMMIT
MICROELECTRONICS, Inc.
Distributed Power Hot-Swap Controller
SMH4812
Preliminary
FEATURES
!
Soft Starts Main Power Supply on Card Insertion
or System Power Up
!
Senses Card Insertion via Short Pins or Ejector
Switches
!
Master Enable to Allow System Control of Power
Up or Down
"
Can be used as a Temperature Sense Input
!
Programmable Independent Controls of a DC/DC
Converter
"
Not Enabled until Host Supply Fully Soft
Started
"
Programmable Time Delay
"
Available Input to hold off Dependant Enables
until Conditions are Satisfied
!
Highly Programmable Circuit Breaker
"
Programmable Quick-Trip
TM
Values
"
Programmable Current Limiting
"
Programmable Duty Cycle Times
"
Programmable Over-current Filter
!
Programmable Host Voltage Fault Monitoring
"
Programmable Under-Voltage Hysteresis
"
Programmable UV/OV Voltage Filter
"
Programmable Fault Mode: Latched or Duty
Cycle
!
Programmable Forced Shutdown Timer
!
2.5V and 5.0V Reference Outputs
"
Eliminates the Need for Other Primary Volt-
ages
"
Easy Expansion of External Monitor Func-
tions
!
Supply Range +20VDC to >+500VDC
SIMPLIFIED APPLICATION DRAWING
0V
Disable/Enable
VDD
Pin Detect
PD1#
ENPG
FS#
FAULT#
UV
SMH4812
OV
PG2#
DC/DC
Pin Detect
PD2#
VSS
CBSENSE VGATE 2.5VREF 5.0VREF
–48V
Characteristics subject to change without notice
2055 4.0 12/22/00
2055 SAD 1.1
©SUMMIT MICROELECTRONICS, Inc., 2000 • 300 Orchard City Dr., Suite 131 • Campbell, CA 95008 • Phone 408-378-3970 • FAX 408-378-6586 • www.summitmicro.com
1
SMH4812
Preliminary
DESCRIPTION
The SMH4812 is designed to control hot swapping of plug-
in cards operating from a single supply, which can have an
output range from 20V to 500V. The SMH4812 hot-swap
controller provides under-voltage and over-voltage moni-
toring of the host power supply, it drives an external power
MOSFET switch that connects the supply to the load, and
it protects against over-current conditions that might dis-
rupt the host supply. When the input and output voltages
to the SMH4812 controller are within specification it pro-
vides a Power Good logic output that may be used to
enable a DC-DC converter. Additional features of the
device include: temperature sense or master enable
input, 2.5V and 5V reference outputs for expanding moni-
tor functions, two Pin-Detect enable inputs for fault protec-
tion, and duty-cycle or latched over-current protection
modes. All of these features can be programmed by the
factory according to the user's requirements.
FUNCTIONAL BLOCK DIAGRAM
ENPG
14
VDD
16
12VREF
PROGRAMM-
ABLE
SHUTDOWN
TIMER
+
13
FS#
12
2.5VREF
DRAIN
1
SENSE
50kΩ
50kΩ
50kΩ
–
11
5.0VREF
EN/TS
3
PD1#
4
PD2#
5
+
–
PROGRAMM-
ABLE
DELAY
15
PG#
UV
9
+
–
FILTER
+
OV
10
5V
12V
2.5V
2
VGATE
VSS
8
PROGRAMM-
ABLE
DELAY
50mV
CBSENSE
7
Programmable
Quick Response
Ref. Voltage
2
–
50kΩ
VGATE
SENSE
+
–
+
–
6
FAULT#
DUTY
CYCLE
TIMER
2055 BD 3.0
2055 4.0 12/22/00
SUMMIT MICROELECTRONICS, Inc.
SMH4812
Preliminary
PIN CONFIGURATION
DRAIN SENSE
VGATE
EN/TS
PD1#
PD2#
FAULT#
CBSENSE
V
SS
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
DD
PG#
ENPG
FS#
2.5V
REF
5V
REF
OV
UV
2055 PCon 2.0
PIN DESCRIPTIONS
DRAIN SENSE (1)
The DRAIN SENSE input monitors the voltage at the drain
of the external power MOSFET switch with respect to V
SS
.
An internal 10µA source pulls the DRAIN SENSE signal
towards the 5V reference level. DRAIN SENSE must be
held below 2.5V to enable the PG outputs.
EN/TS (3)
The Enable/Temperature Sense input is the master en-
able input. If EN/TS is less than 2.5V, VGATE will be
disabled. This pin has an internal 200kW pull-up to 5V.
PD1#, PD2# (4, 5)
These are logic level active low inputs that can optionally
be employed to enable VGATE and the PG outputs when
they are at V
SS
. These pins each have an internal 50kW
pull-up to 5V.
CBSENSE (7)
The circuit breaker sense input is used to detect over-
current conditions across an external, low value sense
resistor (R
S
) tied in series with the Power MOSFET. A
voltage drop of greater than 50mV across the resistor for
longer than t
CBD
will trip the circuit breaker. A program-
mable Quick-Trip sense point is also available.
UV (9)
The UV pin is used as an under-voltage supply monitor,
typically in conjunction with an external resistor ladder.
VGATE will be disabled if UV is less than 2.5V. Program-
mable internal hysteresis is available on the UV input,
adjustable in increments of 62.5mV. Also available is a
filter delay on the UV input.
OV (10)
The OV pin is used as an over-voltage supply monitor,
typically in conjunction with an external resistor ladder.
VGATE will be disabled if OV is greater than 2.5V. A filter
delay is available on the OV input.
VGATE (2)
The VGATE output activates an external power MOSFET
switch. This signal supplies a constant current output
(100µA typical), which allows easy adjustment of the
MOSFET turn on slew rate.
FAULT# (6)
FAULT# is an open-drain, active-low output that indicates
the fault status of the device.
5VREF (11)
This is a precision 5V output reference voltage that may be
used to expand the logic input functions on the SMH4812.
The reference output is with respect to V
SS
.
2.5VREF (12)
This is a precision 2.5V output reference voltage that may
be used to expand the logic input functions on the
SMH4812. The reference output is with respect to V
SS
.
FS# (13)
The Forced Shutdown (FS#) pin is an active low input that
causes VGATE and PG outputs to be shut down at any
time after an internal hold-off timer has expired. The hold-
off timer allows supervisory circuits on the secondary side
(which are not powered up initially) to control shut down of
the SMH4812 via an opto-isolator. This input has no pull-
up resistor.
SUMMIT MICROELECTRONICS, Inc.
2055 4.0 12/22/00
3
SMH4812
Preliminary
ENPG (14)
The ENPG input controls the PG# output. When ENPG is
pulled low the PG# output is immediately placed in a high
impedance state. If ENPG is driven high then the PG#
output will immediately be driven low.
PG# (15)
PG# is an open-drain, active-low output with no internal
pull-up resistor. It can be used to switch a load or enable
a DC/DC converter. PG# is enabled immediately after
VGATE reaches V
DD
– V
GT
and the DRAIN SENSE
voltage is less than 2.5V. Voltage on these pins cannot
exceed 12V, as referenced to V
SS.
V
DD
(16)
V
DD
is the positive supply connection. An internal shunt
regulator connected between V
DD
and V
SS
develops ap-
proximately 12V that supplies the SMH4812. A resistor
must be placed in series with the V
DD
pin to limit the
regulator current (RD in the application illustrations).
V
SS
(8)
V
SS
is connected to the negative side of the supply.
4
2055 4.0 12/22/00
SUMMIT MICROELECTRONICS, Inc.
SMH4812
Preliminary
ABSOLUTE MAXIMUM RATINGS*
Temperature Under Bias ...................... –55°C to 125°C
Storage Temperature ........................... –65°C to 150°C
Lead Solder Temperature (10 secs) ................... 300 °C
Terminal Voltage with Respect to V
SS
:
V
DD
................................. –0.5V to V
DD
OV, UV, DRAIN SENSE,
FS#, CBSENSE ..... –0.5V to V
DD
+0.5V
PD1#, PD2#, ENPG, EN/TS ......... 10V
FAULT#, PG# ........ –0.5V to V
DD
+0.5V
VGATE ................................ V
DD
+0.5V
*COMMENT
Stresses listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions
outside those listed in the operational sections of this specification is not
implied. Exposure to any absolute maximum rating for extended
periods may affect device performance and reliability.
AC OPERATING CHARACTERISTICS
Symbol
Description
Min.
Typ.
5
t
CBD
Programmable 50mV Circuit Breaker delay
(filter)
50
Max.
Units
µs
µs
µs
µs
µs
µs
µs
µs
ms
ms
ms
ms
ns
s
ns
OFF
t
PUVF
Programmable Under-Voltage filter
5
80
160
0.5
t
PDD
Programmable Pin Detect
5
80
*
150
400
50
250
500
1500
5
t
VGD
Programmable Power Good delay
*
20
80
160
t
FSTSHTDN
t
CYC
t
CBRST
Fast shutdown delay from Fault to V
GATE
off
Circuit breaker cycle time
CB
RESET
pulse width
200
200
2.5
*
—
ms
ms
ms
ms
ms
ms
ms
2055 Prog Table
*
160
*
= Default value
SUMMIT MICROELECTRONICS, Inc.
2055 4.0 12/22/00
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