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Ltc3789 chip Chinese information and recommended parameters
The LTC3789 is a high-performance buck-boost switching regulator controller designed to operate with input voltages that can be higher, lower, or equal to the output voltage. It features a constant-frequency, current-mode architecture, offering a phase-lockable frequency of up to 600kHz. This device includes an output current feedback loop for battery charging applications. With a wide input and output range from 4V to 38V (with a maximum of 40V), the LTC3789 ensures seamless and low-noise conversion between different power domains, making it ideal for use in automotive, telecommunications, and battery-powered systems.
In either buck or boost mode, the LTC3789 utilizes a proprietary current-mode control architecture to maintain a consistent frequency, supported by four powerful N-channel MOSFET gate drivers. It also provides an accurate constant-current regulation loop that allows for precise control of input or output current over a broad voltage range. The input current limit feature helps prevent supply overload, while the output current limit offers a stable solution for applications like battery chargers or LED drivers. The device includes comprehensive fault protection against overvoltage, overcurrent, and short-circuit conditions across all operating modes. During shutdown, the LTC3789 disconnects both the input and output voltages.
Users can choose between continuous or pulse skip mode to optimize efficiency at light loads and synchronize the IC with an external clock. Pulse skip mode minimizes ripple under light load conditions, while forced continuous mode maintains a constant frequency, suitable for noise-sensitive applications. The LTC3789 also features an adjustable soft-start function, a power-good output signal, and ±1.5% reference accuracy across a wide temperature range of -40°C to 125°C.
When the output voltage is within 10% of its set point, a power-good signal is generated on the PGOOD pin. The LTC3789 is available in two compact packages: a low-profile 28-pin 4mm x 5mm QFN and a narrow-body SSOP package.
**LTC3789 Pin Description**
The LTC3789 has 28 pins, each serving a specific function critical to its operation:
1. **VFB (PIN1/PIN26)** – Error amplifier feedback pin. This pin receives the feedback voltage from an external resistor divider.
2. **SS (PIN2/PIN27)** – External soft start input. A capacitor connected to this pin controls the rise time of the output voltage.
3. **SENSE+ (PIN3/PIN28)** – Non-inverting input of the current sense comparator.
4. **SENSE- (PIN4/PIN1)** – Inverting input of the current sense comparator.
5. **ITH (PIN5/PIN2)** – Error amplifier output and compensation point. This pin sets the current threshold.
6. **SGND (PIN6/PINS3, EXPOSED PAD PIN29)** – Small signal ground. Must be connected separately to the negative terminal of the input filter capacitor.
7. **MODE/PLLIN (PIN7/PIN4)** – Dual-purpose pin used for mode selection or external synchronization.
8. **FREQ (PIN8/PIN5)** – Frequency setting pin. A resistor connected to this pin adjusts the internal oscillator frequency.
9. **RUN (PIN9/PIN6)** – Run control pin. When pulled below 0.5V, the controller shuts down.
10. **VINSNS (PIN10/PIN7)** – VIN sense input for buck-boost conversion.
11. **VOUTSNS (PIN11/PIN8)** – VOUT sense input for buck-boost conversion.
12. **ILIM (PIN12/PIN9)** – Input/output average current detection pin.
13. **IOSENSE+ (PIN13/PIN10)** – Non-inverting input of the average current sense amplifier.
14. **IOSENSE- (PIN14/PIN11)** – Inverting input of the average current sense amplifier.
15. **TRIM (PIN15/PIN12)** – Must be connected to GND; should not float.
16. **EXTVCC (PIN20/PIN17)** – External power input for INTVCC.
17. **INTVCC (PIN21/PIN18)** – Internal LDO output, powering the control circuitry.
18. **VIN (PIN22/PIN19)** – Main power input pin.
19. **BG1, BG2 (PINS 23, 19/PINS 20, 16)** – Gate drivers for bottom N-channel MOSFETs.
20. **PGND (PIN24/PIN21)** – Drive power ground.
21. **BOOST1, BOOST2 (PINS 25, 18/PINS 22, 15)** – Bootstrap power supplies for top floating drivers.
22. **TG1, TG2 (PIN 26, 17/PIN 23, 14)** – Gate drivers for top N-channel MOSFETs.
23. **SW1, SW2 (PINS 27, 16/PINS 24, 13)** – Switching nodes connected to the inductor.
24. **PGOOD (PIN 28/PIN 25)** – Power good output, indicating when the output voltage is within tolerance.
**Internal Equivalent Circuit of LTC3789**
The LTC3789 operates as a current-mode controller, using a current-sense resistor to monitor inductor current. The ITH pin, which is the output of the error amplifier, controls the current threshold. The VFB pin receives the feedback voltage, which is compared to an internal reference. This allows for precise control of the output voltage, whether it's higher or lower than the input. The device supports both input and output current regulation, ensuring stability and performance in various applications.
**LTC3789 Performance Summary**
- Single inductor architecture
- Supports input voltages above, below, or equal to the output
- Input range: 4V to 38V (max 40V)
- Output range: 0.8V to 38V
- Programmable input or output current limit
- Synchronous rectification
- Up to 98% efficiency
- Integrated MOSFET gate drivers
- 150W output capability
- Output disconnection during shutdown
- PLL-based frequency from 200kHz to 600kHz
- Power good output signal
- ±1.5% reference accuracy over -40°C to +125°C
- Fast transient response and easy loop compensation
- Overvoltage and overcurrent protection
- 5.5V internal and external VCC LDO
**Typical Applications**
The LTC3789 is widely used in automotive power systems, telecom infrastructure, and portable electronics where reliable and efficient power conversion is essential. Its flexible design and robust protection features make it suitable for a variety of challenging environments.