Features

Allow safe insertion and removing circuit boards from the 48V back panel with electricity

working voltage from -10v to -80V

A programmable waves Yong current

Allows 50mA reverse drain piping current

A programmable electronic circuit breaker

Able -proof over pressure protection

Good power control output

Application

Central office transmission switch

-48V distributed power system

negative power supply Control

Instructions

LT #174; 1640AL/LT1640AH are 8 stitches, negative and hydrophilic exchange controllers, so that the circuit board is inserted safely and removed from the active backboard. By controlling the grille voltage of the external N ditbal channel. If the input voltage is less than the programmatic underwriting threshold or greater than the overvoltage threshold. Programmable electronic equipment circuit breaker protection system is exempted from short circuit. This PWRGD (LT1640AL) or PWRGD (LT1640AH) signal can be used to directly enable the power module. LT1640AL is a module with low enable input and LT1640AH for high -enabled input. LT1640AL/LT1640AH provides 8 -needle PDIP and packaged.

Absolutely maximum rated value (Note 1)

Power voltage (VDD -V type) — 0.3 to 100 volts

PWRGD , PWRGD pins -0.3 volts to 100 volts

Disflow -2 volt to 100 volts

induction, door insertion -0.3 volts to 20 volts

UV, OV, OV, OV Pin -0.3 volts to 60 volts

The highest knot temperature 125 degrees Celsius

Work 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 (welding, 10 seconds) 300 degrees Celsius

All voltage refer to VEE

Electric characteristics indicate the specification for the entire operation

The temperature range, otherwise the specifications are TA u003d 25 ° C. Unless otherwise indicated.

Note 1: The absolute maximum rated value means that the value device that exceeds life may be damaged.

Note 2: The current of all entering device pins is positive; the current output from the device is positive. Unless there are other regulations, all voltages are clearly stipulated by VEE.

Typical performance features

Application

PWRGD/PWRGD (pin 1):: Good output pins. This unnecessary switch will be switched when VEE's VPG range. This pinch can be directly connected to the enable pins of the power module. When the discharge of the LT1640AL is higher than the VEE BY, the PWRGD pin will be high impedance. The upper pull current that allows the module to enable the pins will be pulled up and then close the module. When VDrain drops below the VPG, the PWRGD pin absorption current to VEE will be opened and the module will be opened and the module will be opened.

When the drainage of the LT1640AH is higher than the VPG when Vee By, the PWRGD pins will remit the current to the leaky foot of the module with a low pins and force it to leave. When VDrain is lower than VPG, the PWRGD off the leakage current and connect to the 6.5K resistor between PWRGD and drain. The pull current of the module allows the pins to high and open the module.

OV (pin 2): Simulate overvoltage input. When the OV is pulled, it is higher than 1.223V to the high threshold, that is, the condition is detected, and the door sales will immediately lower. The gate of the gate will remain at a low position until OV drops below 1.203V to the low threshold.

UV (pin 3): Simulates the under pressure input. When UV is pulled to 1.223V below the low threshold, the underwriting state is detected, and the door led foot will be pulled immediately. Sales will keep the low level until the ultraviolet rays rose to a low to high threshold higher than 1.243. UV tube foot is also used to reset electronic circuit breaker. If the UV pin gates at the circuit breaker, the reset of the circuit breaker will have a normal power sequence.

Vee (pin 4): negative power supply voltage input. Connect to the low potential of the power supply.

Induction (pin 5): The circuit breaker sensor pins. When you feel that when Vee and induction, the circuit breaker will exceed 50mV in the voltage resistance. The noise peak exceeds 2 μs and is filtered out, which will not make the circuit cut off the circuit breaker. If the cutting current is set to twice the working current of the normal value, only 25MV induced the resistance during normal working resistance. Disable circuit breakers, VEE and Sense can be short -circuited together.

Gate (needle foot 6): The external gate drives output N channel. When the following circumstances, the gate sales will become higher and meet the start -up barPieces: High UV pins, low OV pins and (vsense -vee) lt; 50mv. Gate sales were pulled up 45 μA current source and used 50mA current source.

Discost (pin 7): Simulates leakage input. Connecting the drainage pipe marketing power module of the other N channels and V-pins. When the feet of the drainage pipe are lower than the VPG, the PWRGD or PWRGD pin will be switched. In some cases, drainage is pulled below V. The part is not if the reverse oil sales current is limited to 50mA.

VDD (needle 8): Input of the positive power supply voltage. Connect the high potential pins entered this power supply, and the V+pin of the power module. The voltage range of input power is 10V to 80V.

When the circuit board is inserted into the 48V back panel, the board power input point The router container module or switching power supply generates huge current when charging. The transient current causes permanent damage to the circuit board component and causes a system power supply to fail. The LT1640A design is used to open the power supply control voltage, so that the circuit board is inserted or removed safely from the backplane. The chip also provides under pressure, overvoltage and over -current protection power modules until the input voltage is stable and within the tolerance range.

Power sources

The input of the power module on the board is based on the power path (Figure 6A, all waveforms are sold with the LT1640A). R1 provides current fault detection and R2 can prevent high -frequency oscillation. Resistance R4, R5, and R6 provide underold pressure and overvoltage. By slowly tilting the Q1 door upward, the poured current charging load capacitor C3 and C4 are connected as the circuit board. The resistor R3 and capacitor C2 are accurately controlled by the feedback network. Inspirational flow can be calculated in the following formulas: IINRUSH u003d (45μA CL)/C2, CL is the total load capacitor equal to C3+C4+module input capacitance. The capacitor C1 and resistor R3 prevent the Q1 of Q1 instantly when the power pin is first contacted. Without C1 and R3, the gates of the capacitor C2 can pull Q1 to be equal to VEE C2/CGS (Q1) voltage LT1640A can be powered on and actively pull the gate. The capacitor C1 and the gate are connected to the Q1 capacitor and use the resistor R3 to solve the problem. The value of C1 should be:

Among them, VTH is the minimum grid threshold of MOSFET, and VINMAX is the maximum work input voltage. The value of R3 is not a critical value, and/5 mAh by (vinmax+ #8710; vgate). The waveform is shown in Figure 6b, and it will play several times. When the contacts beating, the LT1640A sense to the under pressure, and the gate was immediately pulled down when the power was disconnected. Once the power pin stops bounce, the door led to the enhancement. As Q1 When opening, the gate voltage remains constant by the feedback network of R3 and C2. When the drain voltage has completed the slope, the gate of the gate gradually becomes its final value.

Electronic circuit breaker

LT1640A has the function of electronic circuit breaker, which can prevent short -circuit or excessive power supply. Place a sensor resistance between the V -tube as the voltage on the inductive resistance of the induction resistance greater than 50mV and exceed 3 μs, as shown in Figure 7. Note that the threshold of the circuit breaker should be set enough to calculate the sum of the load current and the excitation surge. If the load current can control the PWRGD/PWRGD pin (as shown in Figure 6A), the threshold can be set lower because it never needs to adapt to the simultaneous excitation surge and load current. When the trip was broken, the door was immediately pulled to a V -shaped, and the external N channel was closed. Before the circuit breaker is reset, the door led foot will remain at a low level by pulling down the ultraviolet rays, and then high -ultraviolet rays or circulating power to parts. If the mud removal time is required to reject current noise, the external resistance and capacitors can be added to the detection circuit, as shown in Figure 8. As a low -pass filter, R7 and C3 will slow down the speed voltage of the inductive pins too fast. Because the induction needle will source current, usually 20 μA, the voltage will be reduced to R7. This voltage will be included in the barrier -cutting voltage as the voltage of the induction resistance. It is recommended to use small resistors. R7 is 100 #8486; it will cause 2MV errors. You can use the following formula to estimate the delay of the detection pin:

Among them, V (T) is a tracting dealership voltage, usually 50 millivolves. V (to) is before the voltage of the sensor is reduced before the short -circuit or over -current state. When the verb is not as short circuit, the voltage on the induction resistance or the current is applied.

Example: The current load of the system is 1A, 0.02 #8486; The expansion delay circuit needs to be designed as a load jump to 50 μs delay time

5A. In this case:

v (t) ) u003d 20 millivoltors

u003d 5A0.02 #8486; u003d 100 millival

If you choose R u003d 100 #8486;, then C u003d 1 μF.

In some cases, the short circuit of the output end makes the input power below the ultraviolet threshold, and immediately reset the circuit breaker. LT1640A then repeatedly circulate until the short circuit was removed. You can use a capacitor to from UV to Victoria by adding a capacitor. The capacitor and Ultra -ultraviolet resistance allows the input power to restore the Rander Riter before recovering. A circuit current failure of an automatic reset is shown in Figure 9. Crystal tube Q2 and Q3 and R7, R8,C4 and D1 form a programmable disposable circuit. Before the short circuit occurred, the door sales were high, Q3 opened, and the node 2 turned. The resistor R8 is turned off Q2. When one happens, the door led foot is pulled down and the Q3 is closed. Node 2 starts charging C4 and Q2 to open, pull the UV pin low and reset the circuit breaker. Once the C4 is fully charged, the R8 turn off Q2, UV is elevated, and the gate begins to accelerate. Q3 Re -open and quickly pull into the node 2 back to Vee. The diode D1 pinch node 3 A diode drops below V -shaped. The duty occupation ratio is set to 10%to prevent Q1 from overheating.

Impurd and overvoltage detection

UV (pin 3) and OV (pin 2 (pin 2 (pin 2) ) The pins are detected to detect power supply voltage and overvoltage conditions. OV and UV pins are connected to an analog comparator with 20MV lag. When the UV PIN is lower than the threshold of the threshold or OV PIN, the door sales are immediately lowered. This grid's feet will remain at a lower level until UV is high and OV is low. The underwriting voltage and overpowering voltage can be programmed using a three -resistor division. As shown in the medium, it is set to 37V when the pressure threshold is set to 37V when the voltage threshold is set to 71V when the voltage threshold is set to 71V. The resistor division will also enlarge the 20mV lag input terminal at the UV pin and the OV pin of the 20mv pins, respectively 0.6V and 1.2V, respectively. You can add more lag to the UV threshold to connect the resistor R3 between the UV pin and the gate in the UV threshold in the following way.

The new threshold voltage of the new threshold when the input is input:

R1 u003d 562K, R2 u003d 16.9k, R3 u003d 1.62m, vgate u003d 13.5vvuvhy u003d 20mv, the underwriting threshold is 43V (from low to high) and 37.6V (from high to low). This lag is 5.4V. Solid resistor separator is used to set the overvoltage threshold:

When R4 u003d 506K, R5 u003d 8.87k, VOVH u003d 1.223V, the overvoltage threshold is 71V.

PWRGD/PWRGD output

When the input voltage is input to the module, the PWRGD/PWRGD output can be used directly to open the power module within the tolerance range. LT1640AL has PWRGD output for modules with low activation inputs, and LT1640AH has a PWRGD output for high activation input. When the drainage voltage of the LT1640AH is high for VEE (Figure 11), the Q3 of the internal transistor is closed, and the R7 and Q2 clamp the PWRGD pin 1 diode (≈0.7V) or above. Crystal tube Q2The pull current and module of the wave module are closed. When the drain voltage drops below the VPG, the Q3 will be turned on, and the bottom of the R7 will be shortened to the drainage pipe and the Q2 will be turned off. Then, the pull -up current in the module flows over the R7, pulls the PWRGD pin and enables the module.

When the drain voltage of the LT1640AL is high, for VEE, the internal pull -down crystal tube Q2 is closed in Figure 12 is a high impedance state. PWRGD pins will pull the current of the module's internal pull current source and close the module. When the drain voltage is lower than the VPG, the Q2 will turn the PWRGD pin to lower the module. The PWRGD signal can also be used to open the LED or optical isolationer to indicate that the power supply is good, as shown in FIG. 13.

Gate -to -foot pipe voltage adjustment

When the power supply voltage of the chip is greater than 15.5V, the grille's foot voltage is adjusted to 13.5V higher than VEE. If the power supply voltage is lower than 15.5V, the gate voltage will be lower than the power supply voltage about 2 volts. The lowest 10 volt power supply voltage, the gate voltage guarantee is greater than 6V, and the door voltage is not greater than 18V power supply voltage up to 80V.

Differential sales protection

A unique feature of the LT1640A is that it is released. The drainage pipe is designed to bear the voltage (about V) that can withstand the negative electrode. The short -circuit V -shaped tube feet appear on the 48V back panel, but due to the energy storage capacitor C3 (Figure 12), the leak pipe foot is more negative than the V -shaped tube foot. Q1's main diode, plus I R pressure drops on R1 (if R1 is small), keeps the drain below 1.5V dimension. 1.5V reverse voltage generates a 50mA reverse voltage drain current, in LT1640A. The design of R1 is greater than 0.1 #8486; the resistance that connects with the drain feet may not exceed the maximum 50mA leakage current.