LT1640AL/LT1640AH
Negative Voltage
Hot Swap Controller
FEATURES
s
s
s
s
s
s
s
s
DESCRIPTIO
Allows Safe Board Insertion and Removal
from a Live – 48V Backplane
Operates from –10V to – 80V
Programmable Inrush Current
Allows 50mA of Reverse Drain Pin Current
Programmable Electronic Circuit Breaker
Programmable Overvoltage Protection
Programmable Undervoltage Lockout
Power Good Control Output
APPLICATIO S
s
s
s
Central Office Switching
– 48V Distributed Power Systems
Negative Power Supply Control
The LT
®
1640AL/LT1640AH are 8-pin, negative voltage
Hot Swap
TM
controllers that allow a board to be safely
inserted and removed from a live backplane. Inrush cur-
rent is limited to a programmable value by controlling the
gate voltage of an external N-channel pass transistor. The
pass transistor is turned off if the input voltage is less than
the programmable undervoltage threshold or greater than
the overvoltage threshold. A programmable electronic
circuit breaker protects the system against shorts. The
PWRGD (LT1640AL) or PWRGD (LT1640AH) signal can
be used to directly enable a power module. The LT1640AL
is designed for modules with a low enable input and the
LT1640AH for modules with a high enable input.
The LT1640AL/LT1640AH are available in 8-pin PDIP and
SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swap is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
GND
GND
R4
†
562k
1%
UV = 37V
R5
†
9.09k
1%
R6
10k
1%
*
†
(SHORT PIN)
8
V
DD
3
UV
LT1640AL
2
OV
V
EE
4
SENSE
5
C1
†
150nF
25V
4
2
Q1
IRF530
GATE
6
R2
10Ω
5%
R3
†
†
18k C2
3.3nF
5%
100V
2
ON/OFF
1
9
V
OUT+
V
IN+
8
SENSE
+
7
TRIM
–
6
SENSE
4
5
–
V
OUT–
V
IN
LUCENT
JW050A1-E
5V
DRAIN
7
PWRGD
1
CONTACT
BOUNCE
OV = 71V
3
– 48V
1
R1
0.02Ω
5%
†
* DIODES INC. SMAT70A
†
THESE COMPONENTS ARE APPLICATION
SPECIFIC AND MUST BE SELECTED BASED
UPON OPERATING CONDITIONS AND DESIRED
PERFORMANCE. SEE APPLICATIONS
INFORMATION.
C3
0.1µF
100V
+
C4
100µF
100V
+
C5
100µF
16V
1640A TA01
U
Input Inrush Current
1640A F07b
U
U
1
LT1640AL/LT1640AH
ABSOLUTE
MAXIMUM
RATINGS
U
W W
U
W
(Note 1), All Voltages Referred to V
EE
Supply Voltage (V
DD
– V
EE
) .................... – 0.3V to 100V
PWRGD, PWRGD Pins ........................... – 0.3V to 100V
DRAIN Pin ................................................. – 2V to 100V
SENSE, GATE Pins .................................... – 0.3V to 20V
UV, OV Pins .............................................. – 0.3V to 60V
Maximum Junction Temperature ......................... 125°C
Operating Temperature Range
LT1640ALC/LT1640AHC ........................ 0°C to 70°C
LT1640ALI/LT1640AHI ...................... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
PACKAGE/ORDER I FOR ATIO
TOP VIEW
PWRGD 1
OV 2
UV 3
V
EE
4
N8 PACKAGE
8-LEAD PDIP
8
7
6
5
V
DD
DRAIN
GATE
SENSE
ORDER PART
NUMBER
LT1640ALCN8
LT1640ALCS8
LT1640ALIN8
LT1640ALIS8
S8 PART MARKING
1640AL
640ALI
PWRGD 1
OV 2
UV 3
V
EE
4
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 120°C/W (N8)
T
JMAX
= 125°C,
θ
JA
= 150°C/W (S8)
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
DC
V
DD
I
DD
V
CB
I
PU
I
PD
I
SENSE
∆V
GATE
V
UVH
V
UVL
V
UVHY
I
INUV
V
OVH
V
OVL
V
OVHY
I
INOV
Supply Operating Range
Supply Current
Circuit Breaker Trip Voltage
GATE Pin Pull-Up Current
GATE Pin Pull-Down Current
SENSE Pin Current
External Gate Drive
UV Pin High Threshold Voltage
UV Pin Low Threshold Voltage
UV Pin Hysteresis
UV Pin Input Current
OV Pin High Threshold Voltage
OV Pin Low Threshold Voltage
OV Pin Hysteresis
OV Pin Input Current
V
OV
= V
EE
V
UV
= V
EE
PARAMETER
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2), V
DD
= 48V, V
EE
= 0V unless otherwise noted.
CONDITIONS
q
UV = 3V, OV = V
EE
, SENSE = V
EE
V
CB
= (V
SENSE
– V
EE
)
Gate Drive On, V
GATE
= V
EE
Any Fault Condition
V
SENSE
= 50mV
(V
GATE
– V
EE
), 15V
≤
V
DD
≤
80V
(V
GATE
– V
EE
), 10V
≤
V
DD
< 15V
UV Low to High Transition
UV High to Low Transition
OV Low to High Transition
OV High to Low Transition
2
U
TOP VIEW
8
7
6
5
V
DD
DRAIN
GATE
SENSE
W
ORDER PART
NUMBER
LT1640AHCN8
LT1640AHCS8
LT1640AHIN8
LT1640AHIS8
S8 PART MARKING
1640AH
640AHI
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 120°C/W (N8)
T
JMAX
= 125°C,
θ
JA
= 150°C/W (S8)
MIN
10
TYP
MAX
80
UNITS
V
mA
mV
µA
mA
µA
V
V
V
V
mV
µA
V
V
mV
µA
q
q
q
1.3
40
– 30
24
50
– 45
50
– 20
13.5
8
1.243
1.223
20
– 0.02
1.198
1.165
1.223
1.203
20
– 0 .03
5
60
– 60
70
18
15
1.272
1.247
– 0.5
1.247
1.232
– 0.5
q
q
q
q
10
6
1.213
1.198
q
q
q
q
LT1640AL/LT1640AH
ELECTRICAL CHARACTERISTICS
SYMBOL
V
PG
V
PGHY
I
DRAIN
V
OL
PARAMETER
Power Good Threshold
Power Good Threshold Hysteresis
Drain Input Bias Current
PWRGD Output Low Voltage
V
DRAIN
= 48V
PWRGD (LT1640AL), (V
DRAIN
– V
EE
) < V
PG
I
OUT
= 1mA
I
OUT
= 5mA
PWRGD (LT1640AH), V
DRAIN
= 5V
I
OUT
= 1mA
PWRGD (LT1640AL), V
DRAIN
=48V,
V
PWRGD
= 80V
PWRGD (LT1640AH), (V
DRAIN
– V
EE
) < V
PG
q
q
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2), V
DD
= 48V, V
EE
= 0V unless otherwise noted.
CONDITIONS
V
DRAIN
– V
EE
, High to Low Transition
MIN
1.1
10
TYP
1.4
0.4
50
0.48
1.50
0.75
0.05
2
6.5
500
0.8
3.0
1.0
10
MAX
2.0
UNITS
V
V
µA
V
V
V
µA
kΩ
PWRGD Output Low Voltage
(PWRGD – DRAIN)
I
OH
R
OUT
AC
t
PHLOV
t
PHLUV
t
PLHOV
t
PLHUV
t
PHLSENSE
t
PHLPG
t
PLHPG
OV High to GATE Low
UV Low to GATE Low
OV Low to GATE High
UV High to GATE High
SENSE High to Gate Low
DRAIN Low to PWRGD Low
DRAIN Low to (PWRGD – DRAIN) High
DRAIN High to PWRGD High
DRAIN High to (PWRGD – DRAIN) Low
Output Leakage
Power Good Output Impedance
(PWRGD to DRAIN)
q
q
q
Figures 1, 2
Figures 1, 3
Figures 1, 2
Figures 1, 3
Figures 1, 4
(LT1640AL) Figures 1, 5
(LT1640AH) Figures 1, 5
(LT1640AL) Figures 1, 5
(LT1640AH) Figures 1, 5
2
1.7
1.5
5.5
6.5
3
0.5
0.5
0.5
0.5
4
µs
µs
µs
µs
µs
µs
µs
µs
µs
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to V
EE
unless otherwise
specified.
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage
1.8
1.7
SUPPLY CURRENT (mA)
1.6
T
A
= 25°C
1.5
SUPPLY CURRENT (mA)
1.4
1.3
1.2
1.1
1.6
1.5
1.4
1.3
1.2
1.1
0
0
20
80
60
SUPPLY VOLTAGE (V)
40
100
1640A G01
GATE VOLTAGE (V)
U W
Supply Current vs Temperature
V
DD
= 48V
15
14
13
12
11
10
9
8
7
Gate Voltage vs Supply Voltage
T
A
= 25°C
1.0
– 50
– 25
0
25
50
TEMPERATURE (°C)
75
100
1640A G02
6
0
20
80
60
40
SUPPLY VOLTAGE (V)
100
1640A G03
3
LT1640AL/LT1640AH
TYPICAL PERFOR A CE CHARACTERISTICS
Gate Voltage vs Temperature
15.0
14.5
14.0
13.5
13.0
12.5
12.0
– 50
TRIP VOLTAGE (mV)
V
DD
= 48V
GATE PULL-UP CURRENT (µA)
GATE VOLTAGE (V)
– 25
25
50
0
TEMPERATURE (°C)
Gate Pull-Down Current
vs Temperature
55
V
GATE
= 2V
0.5
PWRGD OUTPUT LOW VOLTAGE (V)
GATE PULL-DOWN CURRENT (mA)
OUTPUT IMPEDANCE (kΩ)
52
49
46
43
40
– 50
– 25
0
50
25
TEMPERATURE (°C)
PI FU CTIO S
PWRGD/PWRGD (Pin 1):
Power Good Output Pin. This pin
will toggle when V
DRAIN
is within V
PG
of V
EE
. This pin can
be connected directly to the enable pin of a power module.
When the DRAIN pin of the LT1640AL is above V
EE
by
more than V
PG
, the PWRGD pin will be high impedance,
allowing the pull-up current of the module’s enable pin to
pull the pin high and turn the module off. When V
DRAIN
drops below V
PG
, the PWRGD pin sinks current to V
EE
,
pulling the enable pin low and turning on the module.
When the DRAIN pin of the LT1640AH is above V
EE
by
more than V
PG
, the PWRGD pin will sink current to the
DRAIN pin which pulls the module’s enable pin low,
forcing it off. When V
DRAIN
drops below V
PG
, the PWRGD
sink current is turned off and a 6.5k resistor is connected
between PWRGD and DRAIN, allowing the module’s pull-
up current to pull the enable pin high and turn on the
module.
4
U W
75
1640A G04
Circuit Breaker Trip Voltage
vs Temperature
55
54
53
52
51
50
49
48
– 50
48
47
46
45
44
43
42
41
Gate Pull-Up Current
vs Temperature
V
GATE
= 0V
100
– 25
50
0
25
TEMPERATURE (°C)
75
100
1640A G05
40
– 50
– 25
0
25
50
TEMPERATURE (°C)
75
100
1640A G06
PWRGD Output Low Voltage
vs Temperature (LT1640AL)
8
I
OUT
= 1mA
PWRGD Output Impedance
vs Temperature (LT1640AH)
V
DRAIN
– V
EE
> 2.4V
0.4
7
6
5
4
3
2
– 50
0.3
0.2
0.1
75
100
1640A G07
0
– 50
– 25
25
50
0
TEMPERATURE (°C)
75
100
1640A G08
– 25
0
25
50
TEMPERATURE (°C)
75
100
1640A G09
U
U
U
LT1640AL/LT1640AH
PIN FUNCTIONS
OV (Pin 2):
Analog Overvoltage Input. When OV is pulled
above the 1.223V low-to-high threshold, an overvoltage
condition is detected and the GATE pin will be immediately
pulled low. The GATE pin will remain low until OV drops
below the 1.203V high-to-low threshold.
UV (Pin 3):
Analog Undervoltage Input. When UV is
pulled below the 1.223V high to low threshold, an under-
voltage condition is detected and the GATE pin will be
immediately pulled low. The GATE pin will remain low
until UV rises above the 1.243 low-to-high threshold.
The UV pin is also used to reset the electronic circuit
breaker. If the UV pin is cycled low and high following the
trip of the circuit breaker, the circuit breaker is reset and
a normal power-up sequence will occur.
V
EE
(Pin 4):
Negative Supply Voltage Input. Connect to
the lower potential of the power supply.
SENSE (Pin 5):
Circuit Breaker Sense Pin. With a sense
resistor placed in the supply path between V
EE
and
SENSE, the circuit breaker will trip when the voltage
across the resistor exceeds 50mV. Noise spikes of less
than 2µs are filtered out and will not trip the circuit
breaker.
If the circuit breaker trip current is set to twice the normal
operating current, only 25mV is dropped across the
sense resistor during normal operation. To disable the
circuit breaker, V
EE
and SENSE can be shorted together.
GATE (Pin 6):
Gate Drive Output for the External
N-Channel. The GATE pin will go high when the following
start-up conditions are met: the UV pin is high, the OV pin
is low and (V
SENSE
– V
EE
) < 50mV. The GATE pin is pulled
high by a 45µA current source and pulled low with a
50mA current source.
DRAIN (Pin 7):
Analog Drain Sense Input. Connect this
pin to the drain of the external N-channel and the V
–
pin
of the power module. When the DRAIN pin is below V
PG
,
the PWRGD or PWRGD pin will toggle. In some condi-
tions, the DRAIN pin is pulled below V
EE
. The part is not
damaged if the reverse DRAIN pin current is limited to
50mA.
V
DD
(Pin 8):
Positive Supply Voltage Input. Connect this
pin to the higher potential of the power supply inputs and
the V
+
pin of the power module. The input supply voltage
ranges from 10V to 80V.
BLOCK DIAGRA
UV
REF
OV
–+
V
EE
SENSE
+
–
W
+
+
–
–
U
U
U
V
DD
V
CC
AND
REFERENCE
GENERATOR
V
CC
REF
OUTPUT
DRIVE
PWRGD/PWRGD
50mV
LOGIC
AND
GATE DRIVE
+
+
–
V
EE
V
PG
–
1640A BD
GATE
DRAIN
5
