Electronic Components Datasheet Search |
|
LM5022QDGSTQ1 Datasheet(PDF) 11 Page - Texas Instruments |
|
|
LM5022QDGSTQ1 Datasheet(HTML) 11 Page - Texas Instruments |
11 / 37 page 11 LM5022-Q1 www.ti.com SNVSAG9 – MARCH 2016 Product Folder Links: LM5022-Q1 Submit Documentation Feedback Copyright © 2016, Texas Instruments Incorporated Feature Description (continued) 7.3.3 Error Amplifier An internal high gain error amplifier is provided within the LM5022-Q1. The amplifier’s non-inverting input is internally set to a fixed reference voltage of 1.25 V. The inverting input is connected to the FB pin. In non- isolated applications such as the boost converter the output voltage, VO, is connected to the FB pin through a resistor divider. The control loop compensation components are connected between the COMP and FB pins. For most isolated applications the error amplifier function is implemented on the secondary side of the converter and the internal error amplifier is not used. The internal error amplifier is configured as an open drain output and can be disabled by connecting the FB pin to ground. An internal 5-k Ω pullup resistor between a 5-V reference and COMP can be used as the pull-up for an opto-coupler in isolated applications. 7.3.4 Current Sensing and Current Limiting The LM5022-Q1 provides a cycle-by-cycle over current protection function. Current limit is accomplished by an internal current sense comparator. If the voltage at the current sense comparator input exceeds 0.5 V, the MOSFET gate drive will be immediately terminated. A small RC filter, located near the controller, is recommended to filter noise from the current sense signal. The CS input has an internal MOSFET which discharges the CS pin capacitance at the conclusion of every cycle. The discharge device remains on an additional 65 ns after the beginning of the new cycle to attenuate leading edge ringing on the current sense signal. The LM5022-Q1 current sense and PWM comparators are very fast, and may respond to short duration noise pulses. Layout considerations are critical for the current sense filter and sense resistor. The capacitor associated with the CS filter must be located very close to the device and connected directly to the pins of the controller (CS and GND). If a current sense transformer is used, both leads of the transformer secondary should be routed to the sense resistor and the current sense filter network. The current sense resistor can be located between the source of the primary power MOSFET and power ground, but it must be a low inductance type. When designing with a current sense resistor all of the noise sensitive low-power ground connections should be connected together locally to the controller and a single connection should be made to the high current power ground (sense resistor ground point). 7.3.5 PWM Comparator and Slope Compensation The PWM comparator compares the current ramp signal with the error voltage derived from the error amplifier output. The error amplifier output voltage at the COMP pin is offset by 1.4 V and then further attenuated by a 3:1 resistor divider. The PWM comparator polarity is such that 0 V on the COMP pin will result in a zero duty cycle at the controller output. For duty cycles greater than 50%, current mode control circuits can experience sub- harmonic oscillation. By adding an additional fixed-slope voltage ramp signal (slope compensation) this oscillation can be avoided. Proper slope compensation damps the double pole associated with current mode control (see Control Loop Compensation) and eases the design of the control loop compensator. The LM5022- Q1 generates the slope compensation with a sawtooth-waveform current source with a slope of 45 µA × ƒSW, generated by the clock (see Figure 13). This current flows through an internal 2-k Ω resistor to create a minimum compensation ramp with a slope of 100 mV × ƒSW (typical). The slope of the compensation ramp increases when external resistance is added for filtering the current sense (RS1) or in the position RS2. As shown in Figure 13 and the Functional Block Diagram, the sensed current slope and the compensation slope add together to create the signal used for current limiting and for the control loop itself. |
Similar Part No. - LM5022QDGSTQ1 |
|
Similar Description - LM5022QDGSTQ1 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |