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PDF RT1720 Data sheet ( Hoja de datos )
| Número de pieza | RT1720 | |
| Descripción | 60V Hot Swap Controller | |
| Fabricantes | Richtek | |
| Logotipo |  |
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RT1720
60V Hot Swap Controller with Fault Timer
General Description
The RT1720 is an over-voltage and over-current
protection circuit. It monitors a circuit’s input voltage
and current with its adjustable over-voltage and
over-current thresholds and drives an external
N-MOSFET switch to connect the input to the output
voltage only when it is safe. Its wide input voltage
range makes it useful for high-voltage applications and
in systems that experience large transient voltages and
currents, such as automotive, telecom, and industrial
applications.
During over-voltage events, the RT1720 quickly
reduces the gate drive of the external MOSFET to
regulate the output voltage at the level chosen by its
external FB resistors. During over-current events, when
the load draws excessive current, the RT1720 reduces
the gate drive to regulate the output current at the level
set by its external current sense resistor. In both cases
the output voltage or current is linearly regulated,
thermally stressing the MOSFET load switch. However,
an externally-adjustable timer limits the duration of
MOSFET stress, eventually signaling a fault and then
turning off the MOSFET. The RT1720 then periodically
restarts operation to test if the fault has cleared. The
timer protects the MOSFET while allowing the load
circuit to temporarily operate normally through voltage
and current surges, such as load dump in automobiles
or spinning up disk drives.
The RT1720 features include, open-drain fault and
power-good outputs, and a shutdown input.
The RT1720 is available in the MSOP-10 package.
Features
Wide Input Operation Range : 5V to 80V
Negative Input Voltage Rating to −60V
Adjustable Output Clamp Voltage
Adjustable Over-Current Protection
Programmable Timer for Fault Protection
Low Shut Down Current
Internal Charge Pump N-MOSFET Drive
Fast 80mA MOSFET Shut-off for Overvoltage
Fault Output Indication
Applications
Automotive/Avionic Surge Protection
Hot Swap/Live Insertion
High-Side Switch for Battery Powered Systems
Intrinsic Safety Applications
Simplified Application Circuit
VIN
5V to 80V
RSNS
R3 VCC
SHDN
SNS
GATE
VOUT
RT1720
CTMR
FB
TMR
FLT
PGOOD
GND
Q1 VOUT
VOUT_Max = 60V
COUT
R2
FAULT
POWER
GOOD
R1
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS1720-01 November 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT1720
Absolute Maximum Ratings (Note 1)
VCC, SNS---------------------------------------------------------------------------------------------------------------60V to 90V
S̅̅̅H̅̅D̅̅N̅̅ --------------------------------------------------------------------------------------------------------------------0.3V to 45V
S̅̅̅H̅̅D̅̅N̅̅ Input Current --------------------------------------------------------------------------------------------------- 1mA
VOUT---------------------------------------------------------------------------------------------------------------------0.3V to 65V
GATE------------------------------------------------------------------------------------- 0.3V to VOUT + AMR (GATE to VOUT)
GATE to VOUT --------------------------------------------------------------------------------------------------------(Note 5)
FB, TMR -----------------------------------------------------------------------------------------------------------------0.3V to 10V
F̅̅̅L̅̅T̅̅, PGOOD -----------------------------------------------------------------------------------------------------------0.3V to 12V
TMR, FB, VOUT, GATE, PGOOD, FLT (Note 6)---------------------------------------------------------10mA
Power Dissipation, PD @ TA = 25C
MSOP-10----------------------------------------------------------------------------------------------------------------0.27W
Package Thermal Resistance (Note 2)
MSOP-10, JA----------------------------------------------------------------------------------------------------------365C/W
Lead Temperature (Soldering, 10 sec.)--------------------------------------------------------------------------260C
Junction Temperature ------------------------------------------------------------------------------------------------150C
Storage Temperature Range ---------------------------------------------------------------------------------------65C to 150C
ESD Susceptibility (Note 3)
HBM (Human Body Model) -----------------------------------------------------------------------------------------2kV
MM (Machine Model) -------------------------------------------------------------------------------------------------200V
Recommended Operating Conditions (Note 4)
Supply Input Voltage, VCC ------------------------------------------------------------------------------------------ 5V to 80V
Output Voltage, VOUT ------------------------------------------------------------------------------------------------ 5V to 60V
Ambient Temperature Range--------------------------------------------------------------------------------------- 40C to 85C
Junction Temperature Range --------------------------------------------------------------------------------------40C to 125C
Electrical Characteristics
(VCC = 12V, TA = 25C, unless otherwise specified)
Parameter
VCC Supply Current
Symbol
ICC
Reverse Input Current
IR
GATE Output High Voltage
(Note 5)
VGATE
GATE Pull-Up Current
IGATE_UP
Test Conditions
S̅̅̅H̅̅D̅̅N̅̅ unconnected
S̅̅̅H̅̅D̅̅N̅̅ = GND
VS̅̅̅SH̅̅ND̅S̅N̅̅=
VCC = 30V,
unconnected
VCC = 5V ; (VGATE VOUT)
80V ≥ VCC ≥ 8V ; (VGATE
VOUT)
VGATE = 12V
VGATE = 48V, VCC = 48V
Min
--
--
--
--
--
15
30
Typ Max Unit
2.3 5 mA
7 25 A
0.3 1 mA
9 12
V
12 16
40 60
A
70 120
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS1720-01 November 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
Application Information
The RT1720 over-voltage and over-current protection
controller directly drives an external N-MOSFET load
switch to limit the voltage and current delivered to a
load and to protect the load. If the supply voltage
surges or the load draws excessive current, the
RT1720 controls the MOSFET gate to regulate the
voltage or current, keeping both below their adjustable
thresholds. If any fault condition continues long enough
to for the adjustable-length fault timer to time out, the
MOSFET is turned off for some time and then the
MOSFET automatically turns on again. MOSFET
turn-on is slow and controlled, to prevent surge
currents, making the circuit useful for soft-start and hot
insertion applications.
Fault Timer
The RT1720’s fault timer is activated during any
over-voltage or over-current event. During an event,
the capacitor at TMR (CTMR) is slowly charged. When
the voltage at TMR reaches 1.2V, the open-drain
F̅̅̅L̅̅T̅ output goes low and when VTMR reaches 1.4V the
MOSFET switch is turned off disconnecting the load.
The time delay while VTMR charges from 1.2V to 1.4V
gives system software an opportunity to perform any
required housekeeping functions. The fault timing is set
by the external capacitor at TMR.
During an over-voltage fault, the MOSFET load switch
is used to regulate the output voltage at the voltage
level set by the FB resistive divider. During an
over-current fault the current is regulated at the current
level set by the current sense resistor at SNS. In both
of these events, regulating the output voltage or current
causes power dissipation in the external MOSFET load
switch. The fault timer sets the maximum duration of
the power dissipation stress. Select CTMR to keep the
MOSFET power dissipation acceptable for the selected
external MOSFET. If the MOSFET can withstand
continuous dissipation for any possible fault, you can
disable the timer by connecting TMR to ground.
When the fault timer reaches 1.4V and turns off the
MOSFET, or if the fault ends before VTMR reaches
1.4V, TMR slowly discharges the capacitor (CTMR). If
the fault timer reaches 1.4V, the MOSFET load switch
is turned off to allow the switch and the load to cool
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS1720-01 November 2015
RT1720
while CTMR is slowly discharged. The discharge is
slower than the charge rate to reduce the overall duty
factor for faults that last multiple TMR cycles. Once
VTMR reaches 0.5V, F̅̅̅L̅̅T̅ is released and the MOSFET
turns on again in a controlled soft-start.
The duration of a fault before the MOSFET turns off is :
tFAULT
=
CTMR 1.4V
25μA
The interval between F̅̅̅L̅̅T̅ asserting low and the
MOSFET turning off is given by :
tWARNING
=
CTMR 1.4V
25μA
- 1.2V
The MOSFET cool down period is given by :
tCOOLOFF
=
CTMR 1.4V
3μA
-
0.5V
Over-Voltage Protection
The RT1720’s adjustable over-voltage protection
function uses an external voltage divider at FB, from
the output voltage to GND, to set the protection
threshold voltage. When the voltage at FB exceeds
1.25V (typical), GATE is discharged sharply and the
MOSFET begins turning off. As the MOSFET turns off
and the voltage at FB drops, GATE begins charging up
again. In this way, GATE reaches an equilibrium point
and the output voltage is linear-regulated with FB at
1.25V.
During an over-voltage event, TMR begins charging
while the over-voltage remains and GATE continues to
linear-regulate the output voltage. Eventually, VTMR
may reach 1.2V (where the F̅̅̅L̅̅T̅ output goes low,
signaling a fault) and then 1.4V (where GATE will turn
completely off). If VTMR does not reach 1.4V and the
input voltage drops (allowing GATE to turn on fully),
TMR will slowly discharge. The capacitor at TMR
determines how long an over-voltage event may last
without causing GATE to turn off and the output voltage
to collapse completely.
The system operates normally while TMR charges
during an over-voltage event but the excess input
voltage is dropped across the external MOSFET and
heat is dissipated. The capacitor at TMR should be
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet RT1720.PDF ] | |
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