Texas Instruments develops analog, digital signal processing, RF and DLP® semiconductor technologies that help customers deliver consumer and industrial electronics products with greater performance, increased power efficiency,LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7 higher precision, more mobility and better quality.Texas Instruments Incorporated combines innovative digital signal processor (DSP) and analog technologies to meet customers' real-world signal processing requirements for a broad range of communications, computing, consumer electronics, industrial and automotive applications. In addition to silicon technology, TI provides software and systems expertise enabling customers to differentiate their products. As signal processing and analog solutions are applied in ever more creative ways, TI technology helps customers develop products that make people's lives convenient, productive, secure and fun,LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7

Reducing Overall Power Budget
Most portable, battery-powered, wireless applications (mobile phones, portable consumer electronics, notebooks or any portable equipment with WLAN,LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7 Bluetooth or any other wireless protocol) and a growing number of non-battery-powered applications deployed in the field (like RF microwave subsystems) face the challenge of managing their unused subsystem power consumption. The goal is to optimize their power budget while complying with severe space and cost constraints.LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7

A popular and simple option to reduce the system’s overall power budget is to shut-off subsystems not in use. This can be done easily by placing a load switch on the power rail to connect and disconnect the rail when required. LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7,For instance, a WLAN power module can be disabled while unused and, therefore, eliminate current losses due to subsystem leakages. In a similar way, an emerging number of mobile phone manufacturers tend to disable the RF power amplifier when unused as its represents a reasonable amount of leakage. In communications infrastructure applications, some subsystems can be shut-off during the night to reduce overall leakages when the amount of processing required isn’t as high as during the day.LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7

ON-resistance Specification
ON-resistance is clearly a critical specification as it determines the dropout seen through the FET. An application with low-current ratings (LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7 In addition to the maximum continuous current the designer targets to switch, it is crucial to consider what the maximum pulsed-current is that the switch can accept.LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7 In wireless applications some loads consist of moderate continuous currents followed by current bursts due to the RF power amplifiers. A good example is the GSM/GPRS transmit burst that sinks up to 1.7A during 576µS with a duty cycle of 12.5 percent. It is important to scale the design to comply with such pulsed current.LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7

The UCC3915 programmable hot swap power manager provides complete power-management, hot-swap capability, and circuit breaker functions. The only external component required to operate the device, other than power supply bypassing, LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7 is the fault-timing capacitor, CT. All control and housekeeping functions are integrated,and externally programmable. These include the fault current level, maximum output sourcing current, maximum fault time, and startup delay. In the event of a constant fault, the internal fixed 2% duty cycle ratio limits average output power.The internal 4-bit DAC allows programming of the fault-level current from 0 A to 3 A with 0.25-A resolution.LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7 The IMAX control pin sets the maximum-sourcing current to 1 A above the trip level or to a full 4 A of output current for fast output capacitor charging. (continued)

When the output current is below the fault level, the output MOSFET is switched on with a nominal ON resistance of 0.15 Ω. When the output current exceeds the fault level, but is less than the maximum-sourcing level, the output remains switched on, but the fault timer starts, charging CT. Once CT charges to a preset threshold, the switch is turned off, and remains off for 50 times the programmed fault time.LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7 When the output current reaches the maximum sourcing level, the MOSFET transitions from a switch to a constant current source.The UCC3915 can be put into sleep mode, drawing only 100 μA of supply current. Other features include an open-drain fault-output indicator, thermal shutdown, undervoltage lockout, 7-V to 15-V operation, and low-thermal resistance SOIC and TSSOP power packages.LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7

Although the UCC3915 is designed to provide system protection for all fault conditions, all integrated circuits can ultimately fail short. For this reason, if the UCC3915 is intended for use in safety-critical applications where UL or some other safety rating is required, a redundant safety device such as a fuse should be placed in series with the device. LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7The UCC3915 will prevent the fuse from blowing for virtually all fault conditions, increasing system reliability and reducing maintenance cost, in addition to providing the hot-swap benefits of the device. This Schottky barrier diode bus-termination array is designed to reduce reflection noise on memory LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7 bus lines. This device consists of a 16-bit high-speed Schottky diode array suitable for clamping to VCC and/or GND. The SN74S1053 is characterized for operation from 0°C to 70°C.Diode terminations have several advantages when compared to resistor termination schemes.LM2677T-5.0/NOPB Texas Instruments IC REG BUCK 5V 5A TO220-7  Split resistor or Thevenin equivalent termination can cause a substantial increase in power consumption. The use of a single resistor to ground to terminate a line usually results in degradation of the output high level, resulting in reduced noise immunity.Series damping resistors placed on the outputs of the driver reduce negative transients, but they also can increase propagation delays down the line, as a series resistor reduces the output drive capability of the driving device. Diode terminations have none of these drawbacks.