HV311_09 Datasheet, PDF (1/17 Pages) Supertex, Inc – Hot Swap Controller

HV311
Hot Swap Controller
Features
► 10 to 90V operation, positive or negative
supply
► UV/OV lock out & power-on-reset
► Circuit breaker
► 100ms startup timer
► Automatic retry or latched operation
► Low Power, 400µA sleep mode
► Active low power good
► 8-Lead SOIC package
General Description
The Supertex HV311 Hot Swap Controller provides inrush current limiting and
other power supply support functions for hot swap equipment. Current limiting is
provided by control of an external MOSFET which is placed in the return line of
the power supply connection. Placement in the return allows use of an N-channel
MOSFET without the need for high side driving.
An internal clamp at the GATE pin activates when full bias for the HV311 is not
available, thus keeping the MOSFET in the off-state during the initial insertion
phase. As soon as adequate bias is available for the main control circuits, the UV
(undervoltage) and OV (overvoltage) pins check for normal operating voltage on
the power supply input.
Applications
► 48V central office switching
► 24V cellular and fixed wireless systems
► 24V PBX systems
► Line cards
► 48V powered ethernet for VoIP
► Distributed power systems
► Power supply control
► 48V storage networks
► Electronic circuit breaker
Once normal operating voltage is present, the GATE voltage for the external
MOSFET ramps up at a constant rate. The rate is controlled by the value of an
external capacitor placed at the RAMP pin. At some point the external MOSFET
channel is enhanced, allowing power supply current to flow, thereby energizing
downstream power supply capacitors.
During the GATE ramp up the power supply current is monitored with the aid
of an external sense resistor which forces reduction in the ramp rate when the
power supply current reaches a set limit. The limit is set by the value of the
external sense resistor and the threshold of the current sense amplifier (50mV).
Once inrush current subsides, the GATE voltage resumes its rise to the output
voltage of an internal regulator V_REG, with an output voltage ranging from 8.5
to 12V. When GATE is within 1.2V of V_REG, GATE is pulled high to V_REG with an
internal switch, the open-drain PWRGD pin pulls low, and the HV311 enters a
low power mode.
Typical Application Circuit
The HV311 includes a start-up timer and a circuit breaker function to protect
the MOSFET from excessive power dissipation. The start-up timer trips when
the start-up phase exceeds 100ms. The circuit breaker trips at double the
current limit threshold (100mV). Upon tripping of either the start-up timer or
the circuit breaker the MOSFET is turned off, and the PWRGD pin becomes
high impedance. Thereafter, a programmable automatic retry timer allows the
MOSFET to cool down before resetting and restarting. The automatic retry can
be disabled by adding an external resistor at the RAMP pin (about 2.5MΩ, see
applications section).
GND
8
R1
487kΩ
R2
6.81kΩ
VDD
3 _UV
2 _OV
PWRGD ₁
HV311
ENABLE
C_LOAD
DC/DC
PWM
CONVERTER
+5.0V
COM
R3
9.76kΩ
-48V
VEE
4
SENSE
5
R4
12.5mΩ
GATE RAMP
6
7
C1
10nF
-48V
Q1
IRF530
NOTES:
1. Undervoltage threshold (UV) set to 35V.
2. Overvoltage threshold (OV) set to 65V.
3. Startup current set to 4A.
4. Circuit breaker set to 8A.
5. 100ms max startup time.
6. Automatic retry enabled.
● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: [phone] ● www.supertex.com