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PDF LT1640AL Data sheet ( Hoja de datos )
| Número de pieza | LT1640AL | |
| Descripción | Negative Voltage Hot Swap Controller | |
| Fabricantes | Linear | |
| Logotipo |  |
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FEATURES
s Allows Safe Board Insertion and Removal
from a Live – 48V Backplane
s Operates from –10V to – 80V
s Programmable Inrush Current
s Allows 50mA of Reverse Drain Pin Current
s Programmable Electronic Circuit Breaker
s Programmable Overvoltage Protection
s Programmable Undervoltage Lockout
s Power Good Control Output
U
APPLICATIO S
s Central Office Switching
s – 48V Distributed Power Systems
s Negative Power Supply Control
LT1640AL/LT1640AH
Negative Voltage
Hot Swap Controller
DESCRIPTIO
The LT®1640AL/LT1640AH are 8-pin, negative voltage
Hot SwapTM 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
UV = 37V
OV = 71V
*
(SHORT PIN)
GND
R4†
562k
1%
R5†
9.09k
1%
R6†
10k
1%
3
UV
2
OV
VEE
4
SENSE
5
– 48V
R1†
3
0.02Ω
5%
4
12
* DIODES INC. SMAT70A
† THESE COMPONENTS ARE APPLICATION
SPECIFIC AND MUST BE SELECTED BASED
UPON OPERATING CONDITIONS AND DESIRED
PERFORMANCE. SEE APPLICATIONS
INFORMATION.
8
VDD
LT1640AL
1
PWRGD
GATE
DRAIN
67
C1†
150nF
25V
R2
10Ω
R3†
18k
C2†
5% 5% 3.3nF
100V
Q1
IRF530
C3 +
0.1µF
100V
C4
100µF
100V
2
1
ON/OFF
VIN+
VOUT+
SENSE +
9
8
TRIM 7
SENSE – 6
4 VIN–
VOUT– 5
+
5V
C5
100µF
16V
LUCENT
JW050A1-E
1640A TA01
Input Inrush Current
CONTACT
BOUNCE
1640A F07b
1
1 page  
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.
VEE (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 VEE 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, VEE 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 (VSENSE – VEE) < 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 VPG,
the PWRGD or PWRGD pin will toggle. In some condi-
tions, the DRAIN pin is pulled below VEE. The part is not
damaged if the reverse DRAIN pin current is limited to
50mA.
VDD (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
50mV
–+ –
+
VEE SENSE
VDD
VCC AND
REFERENCE
GENERATOR
VCC
REF
OUTPUT
DRIVE
PWRGD/PWRGD
LOGIC
AND
GATE DRIVE
GATE
+–
+– VPG
VEE
DRAIN
1640A BD
5
5 Page 
LT1640AL/LT1640AH
APPLICATIO S I FOR ATIO
Undervoltage and Overvoltage Detection
The UV (Pin 3) and OV (Pin 2) pins can be used to detect
undervoltage and overvoltage conditions at the power
supply input. The UV and OV pins are internally connected
to analog comparators with 20mV of hysteresis. When the
UV pin falls below its threshold or the OV pin rises above
its threshold, the GATE pin is immediately pulled low. The
GATE pin will be held low until UV is high and OV is low.
The undervoltage and overvoltage trip voltages can be
programmed using a three resistor divider as shown in
Figure 10a. With R4 = 562k, R5 = 9.09k and R6 = 10k, the
undervoltage threshold is set to 37V and the overvoltage
threshold is set to 71V. The resistor divider will also
amplify the 20mV hysteresis at the UV pin and OV pin to
0.6V and 1.2V at the input, respectively.
More hysteresis can be added to the UV threshold by
connecting resistor R3 between the UV pin and the GATE
pin as shown in Figure 10b.
(SHORT PIN)
GND
GND
R4
( )VUV
=
1.223
R4 + R5+ R6
R5 + R6
R5
( )VOV
=
1.223
R4
+ R5+
R6
R6
R6
– 48V
8
3
UV
VDD
LT1640AL
2 LT1640AH
OV
VEE
4
1640A F10a
Figure 10a. Undervoltage and Overvoltage Sensing
(SHORT PIN)
GND
GND
R4
506k
1%
UV = 37.6V
UV = 43V
OV = 71V
R1
562k
1%
R5 R2
8.87k 16.9k
1% 1%
*
– 48V
* DIODES INC. SMAT70A
R3
1.62M
1%
8
VDD
2
OV
3
UV
LT1640AL /LT1640AH
VEE SENSE
GATE
45
6
R1
3
0.02Ω
5%
4
C1
150nF
25V
R6
10Ω
5%
12
Q1 1640A F10b
IRF530
Figure 10b. Programmable Hysteresis for Undervoltage Detection
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT1640AL.PDF ] | |
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