LT4322 AD | Alldatasheet
Document overview
- Manufacturer or author: Analog Devices, Inc.
- PDF pages: 29
Technical content
analog.com Rev. 0 2 of 29 TABLE OF CONTENTS Capacitively Loaded Full-Bridge Applications and VDDA
REVISION HISTORY
02/2023 - Rev. 0: Initial Release
Table 1. Electrical Characteristics
analog.com Rev. 0 4 of 29 (TJ = -40°C to +150°C for the minimum and maximum values. TJA = 25°C for the typical values. VCATHODE = VVDDC = VVDDA = 12V, VVSSA = VANODE = 0V unless otherwise noted.) PARAMETER SYMBOL CONDITIONS/COMMENTS MIN TYP MAX UNITS GATE Drive Output Low Voltage ΔVGATE(L) CATHODE = 12V, IGATE = 1mA 5 50 mV Propagation Delay, CATHODE to GATE Rising to 4V tD,RISE CATHODE = Step 1.5V to -0.2V, CGATE = 10nF 550 1000 ns CATHODE = Step 1.5V to -0.2V, CGATE = 100nF 870 1500 GATE Rise Time, 1V to 4V tRISE CATHODE = Step 1.5V to -0.2V, CGATE = 10nF 370 650 ns CATHODE = Step 1.5V to -0.2V, CGATE = 100nF 550 900 Propagation Delay, CATHODE to GATE Falling to 2V tD,FALL CATHODE = Step -0.1V to 0.1V, CGATE = 10nF 130 260 ns CATHODE = Step -0.1V to 0.1V, CGATE = 100nF 330 660 GATE Fall Time, 9V to 2V tFALL CATHODE = Step -0.1V to 0.1V, CGATE = 10nF 10 45 100 ns CATHODE = Step -0.1V to 0.1V, CGATE = 100nF 85 170 350 1 All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to VSSA unless otherwise specified. VSSA is the device ground and substrate. 2 The maximum VDDC to VSSA operating voltage is 60V. Users can add an external high-voltage depletion N-Channel MOSFET to operate with input voltages above 60V. See the Operation at Voltages Above 60V section for more details. 3 The minimum peak voltage of the VDDC input AC signal with respect to VSSA must ensure that the VDDA voltage always exceeds 9V. The minimum VDDC peak voltage will depend upon application circuit architecture, parasitic input inductance between the AC input supply and the VDDC pin, and VDDA hold-up capacitor value. 4 A DC supply voltage can be used to power the VDDA pin directly. In that case, the VDDC pin must be connected to VSSA.
Table 2. Absolute Maximum Ratings for extended periods may affect product reliability.
Figure 18. Block Diagram in the application circuit. The operation is best understood by referring to the block diagram in Figure 18. GATE voltage low to turn off the MOSFET. VDDA. The LT4322 draws power from VDDC and regulates 12V on VDDA. in the forward mode of operation, where the VDDC voltage is very low.
Figure 20. Four-Diode, High-Voltage Full-Bridge Application, 120VRMS, 60Hz a half-wave rectifier application.
Figure 21. LT4322 in a 48VP-P, 60Hz, 1A Half-Wave Rectifier Application recommended PCB layout techniques. VDDA with a DC input supply, connect a 1µF or larger capacitor between VDDA and VSSA and connect VDDC to VSSA. body diode current rating IS and the single pulse avalanche energy rating EDS,AL(R). robustness during momentary drain-to-source overvoltage conditions.
analog.com Rev. 0 14 of 29 RDS(ON) < 100 mV/IAVG (2) For AC full-bridge rectifier applications, use: RDS(ON) < 100 mV/(3 × IAVG) (3) The AC input calculation assumes the duration of the current conduction occupies 1/3 of the AC period. For very high output current applications, users may connect several MOSFETs in parallel to reduce the overall RDS(ON). The LT4322’s high -speed tran sconductance (GM AMP) amplifier is capable of driving up to 100nF MOSFET gate capacitance at frequencies up to 100kHz. At initial power-up, the application output capacitance is initially charged via the body diode of the power MOSFET until the LT4322 has enough supply voltage to properly control the MOSFET gate. Ensure the MOSFET has a sufficient continuous body diode current rating IS to handle the current at startup. The LT4322’s GATE drive ranges from 10V to 14V when powered from VDDC input supply voltages greater than or equal to 15V. When powered directly from VDDA, the GATE drive voltage equals the VDDA voltage. VGS(TH) must be a minimum of 2V or higher. A gate threshold voltage lower than 2V is not recommended because too much time is needed to discharge the gate below the threshold and halt reverse current conduction when the input AC voltage falls below the CATHODE output voltage. GATE Capacitor Selection The GM amplifier is optimally compensated with 10nF capacitance between the gate and source of the external power MOSFET. For applications using MOSFETs with CISS less than 10nF and/or when voltage peaking is observed in the GATE waveform, adding a 10nF ceramic capacitor CGATE directly across the gate and source of the external power MOSFET can greatly improve the stability of the forward regulation voltage. This comes at the expense of the added charge needed to enhance the gate of the external MOSFET. For high output current and/or high frequency applications where the circuit is rarely in forward regulation, this capacitor can be omitted. Output Capacitor COUT Selection Capacitance COUT is needed across the application output voltage and system ground to provide the output load current for the majority of the AC period. Downstream power needs and voltage ripple tolerance determine how much capacitance is required. C OUT in the hundreds to thousands of microfarads is common. A combination of electrolytic and ceramic capacitors is used to optimize capacitance ESR while minimizing cost. Add a 1 µF ceramic capacitor from the output to the ground near the LT4322 if the bulk electrolytic capacitors are physically remote from the LT4322. For full-wave rectifier applications, a good starting point is selecting COUT such that: COUT ≥ IAVG/(VRIPPLE × 2 × Freq) (4) Where IAVG is the average output load current, VRIPPLE is the maximum tolerable output ripple voltage, and Freq is the frequency of the AC input source. For example, in a 60Hz, 24V application where the load current is 1A and the tolerable ripple is 15V, choose: COUT ≥ 1A/(15V × 2 × 60Hz) = 556µF (5) For half-wave rectifier applications, use: COUT ≥ IAVG/(VRIPPLE × Freq) (6) Users must also ensure that the RMS current in the electrolytic capacitors does not exceed the maximum ripple current rating so that the capacitor’s lifetime is not compromised. An electrolytic capacitor’s ripple current rating is a function of RMS current, frequency, and ambient temperature. Consult the manufacturer’s specifications and ensure
the diode-OR output voltage is not perturbed. Figure 30. DC Diode-OR Application Circuit: Flyback Circuitry Provides Refresh Power to Floating-Ideal Diode Architecture
Figure 33. Two Diode, Full-Wave Rectifier with Center-Tapped Transformer, 120V, 60Hz Line Input, 17V DC Output
Figure 34. High-Speed Four-Diode Full-Bridge Application Circuit, 100VP-P, 100kHz, 3A
Figure 35. High-Voltage Four-Diode Full-Bridge Application Circuit, 300VP-P, 60Hz, 0.5A
Figure 36. Six LT4322’s in a 3-Phase Alternator Application
Figure 37. 8-Lead, 3mm x 3mm, Side Wettable DFN
0.200 REF
1.50 REF
0.275 REF
0.50 BSC
- ALL DIMENSIONS ARE IN MILLIMETERS
- DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
- EXPOSED PAD SHALL BE SOLDER PLATED
- SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
0.203 REF
0.05 REF
0.10 REF
Figure 38. 8-Lead MSOP
Table 4. Ordering Guide Table 5. Related Parts Table 6. Evaluation Boards
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