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The TPS2211A PC Card Power Interface Switch provides an integrated power management solution for a single PC Card. All discrete power mosfets, logic sections, current limiting and PC card controlled thermal protection are combined on a single integrated circuit using Texas Instruments LinBiCMOS process.

12-V card power supply, compatible with many PCMCIA controllers.

The current limiting feature eliminates the need for fuses, reducing component count and improving reliability. Current limit reports can help users isolate system faults to the PC card. controller. The current limiting feature eliminates the need for fuses, reducing component count and improving reliability. Current limit reports can help users isolate system faults to the PC card.

The TPS2211A uses a 3.3-V low voltage mode that allows 3.3-V switching without requiring 5 V. Bias power is available from a 3.3-V or 5-V input. This helps in low-power system designs, such as sleep mode and pager mode, where only 3.3V is available.

Terminal devices for the TPS2211A include notebook computers, desktop computers, personal digital assistants (PDAs), digital cameras, and barcode scanners.

Typical PC Card Power Distribution Application

For selection of suitable capacitors on the power input, see Power Supply Considerations in the Application Information.

Parameter measurement information

application information

Overview

PC Cards were originally developed as a means to add EEPROM (flash memory) to the limited onboard memory of portable computers. The idea of plug-in cards quickly caught on; modems, wireless LANs, GPS systems, multimedia, and hard disk versions soon followed. As the number of PC Card applications grew, the engineering community quickly recognized the need for a standard to ensure cross-platform compatibility. To this end, PCMCIA (Personal Computer Memory Card International Association) was formed with members from leading computer, software, PC card and semiconductor manufacturers. A key goal is to implement the plug-and-play concept, where cards and hosts from different vendors should be compatible.

PC Card Power Specifications

System compatibility also means power supply compatibility. The latest specification (PC Card Standard) developed by the PCMCIA committee states that power will be transferred between the host and the card through 8 of the 68 terminals of the PC Card connector. This power interface consists of two V, two V, and four ground terminals. Multiple V and ground terminals minimize header termination and line resistance. The two V terminals were originally designated as separate signals, but are usually connected together in the mainframe to form a single node to minimize voltage losses. Card main power is supplied through the V terminal; flash programming and erasing voltages are supplied through the V terminal. Cocos Polypropylene Cocos Polypropylene Cocos Polypropylene

Voltage Regulation Design

The current PCMCIA specification has an output voltage regulation of 5% (250 mV) for a 5-V output. In a typical PC power system design, the output voltage regulation (V) of the power supply is 2% (100mv). Additionally, the voltage drop from the power supply to the PC card is caused by resistive losses (V) in the PCB traces and PCMCIA connectors. Typical designs limit the sum of these resistive losses to less than 1% (50 mV) of the output voltage. Therefore, the allowable voltage drop (V) for the TPS2211 is the PCMCIA voltage regulation minus the power supply regulation, and the PCB and connector resistance drop: PS (registered) Printed Circuit Board DS Corporation

Typically, this results in an allowable voltage drop of 100 mV for the TPS2211A. The voltage drop is the output current times the switch resistance of the TPS2211. Therefore, the maximum output current that can be delivered to the PC card in regulation is the allowable voltage drop across the tps211a divided by the output switch resistance.

The AVCC output outputs 1 A continuously over the regulated range of 5 V and 3.3 V over the operating temperature range. Using the same equation, the PCMCIA specification regulates the output voltage to 300mv for a 3.3v output. Using the percent voltage drop for power regulation (2%) and the percent loss in PCB resistance (1%), the allowable voltage drop for a 3.3 V switch is 200 mV. The 12-V output (AVPP) of the TPS2211A can output 150 mA continuously.

Overcurrent thermal protection

Personal computer cards are inherently prone to damage due to improper handling. The host system needs to protect the card from short circuits that can cause damage to the power supply or PCB traces. Even if the system is strong enough to withstand a short circuit, the battery can quickly discharge into a damaged PC card, causing the system to lose power suddenly. Most mainframes are equipped with fuses for protection. Fuse systems are less reliable, and when a fuse blows, it usually requires troubleshooting and repair from the manufacturer.

The TPS2211A uses sense FETs to check for overcurrent conditions in each AVCC and AVPP output. Unlike sense resistors or multi-fuses, these FETs do not increase the series resistance of the switch, thus reducing voltage and power losses. Overcurrent sensing is applied to each output individually. When an overcurrent condition is detected, only the affected power output is limited; all other power outputs continue

functioning normally. When an overcurrent condition is detected, the OC indicator (usually a logic high) is logic low to initiate system diagnostics and/or send a warning message to the user.

During power-up, the TPS2211A controls the rise time of the AVCC and AVPP outputs and limits current to the faulty card or connector. If a short circuit is applied after the power supply is established (for example, hot-inserting a bad card), the current is initially limited only by the impedance between the short circuit and the power supply. In extreme cases, as much as 10A to 15A can flow into the short circuit before the TPS2211A's current limit turns on. If the AVCC or AVPP outputs are driven below ground, the tps211a can latch non-destructively in the off state. Cycling power returns to normal operation.

The overcurrent limit of the AVCC output is designed to activate at power-up short circuit in the 1A to 2.5A range (typically around 1.6A). AVPP output is limited between 180MA and 400MA, usually around 280MA. The protection circuit works by linearly limiting the current through the switch rather than initiating a complete shutdown of the power supply. Only shuts down during thermal limitations.

Thermal limits prevent damage to the integrated circuit due to overheating if the package power dissipation rating is exceeded. Thermal throttling will disable power delivery until the device cools down.

application information

No 12 volt power required

Most PC card switches use an externally provided 12v power supply to drive the gate drive and other chip functions, which requires that power is always present. The TPS2211A provides considerable power savings by using an internal charge pump to generate the required higher voltage from the 5-V input. Therefore, the external 12V supply can be disabled unless required by the flash function, thereby extending battery life. Do not ground the 12-V switch input when the 12-V input is not in use. During software shutdown, the TPS2211A achieves additional power savings, where the quiescent current is reduced to a maximum of 1 µA.

3.3-V low voltage mode

When 3.3V is the only available input voltage (V=0), the TPS2211A operates in 3.3V low voltage mode. This allows the host and PC card to operate in low power modes at 3.3 volts, such as sleep or pager mode. Note that in these modes of operation, the TPS2211A gets its bias current from the 3.3-V input pins, and only 3.3 V can be delivered to the PC card. I (5V)

Voltage Conversion Requirements

PC cards are migrating from 5V to 3.3V to minimize power consumption, optimize board space, and increase logic speed. The TPS2211A complies with all power delivery combinations currently defined in the PCMCIA standard. The latest protocol supports mixed 3.3-V/5-V systems by first supplying the card with 5 V and then polling it for 3.3-V compatibility. The PCMCIA specification requires that capacitors on 3.3-V compliant cards be discharged below 0.8 V before using a 3.3-V power supply. This acts as a power reset and ensures that sensitive 3.3V circuits are not affected by any remaining 5V charge. The TPS2211A provides selectable V and V ground states according to the PCMCIA 3.3-V/5-V switching specification. Cocos Islands Polypropylene

output ground switch

The PC Card specification requires V to discharge within 100ms. Because power management schemes can create high impedance isolation, PC Card resistors cannot be relied upon to provide a discharge path for voltages stored on PC Card capacitors. cocos islands

Power Considerations

The TPS2211A has multiple pins for both the 3.3-V and 5-V power supply inputs and the switch AVCC output. Any individual pin can conduct rated input or output current. Unless all pins are connected in parallel, the series resistance is significantly higher than specified, resulting in increased voltage drop and power loss. Parallel connection of all input and output power pins is recommended for optimal operation.

To improve the noise immunity of the TPS2211A, the power input should be bypassed with a 4.7-µF or larger electrolytic or tantalum capacitor and placed in parallel with a 0.1-µF ceramic capacitor. Bypassing the switching output with a 0.1-micron or larger ceramic capacitor is strongly recommended; doing so improves the TPS2211A's immunity to electrostatic discharge (ESD). Care should be taken to minimize the PCB trace inductance between the TPS2211A and the load. High switching currents produce large negative voltage transients that forward bias the substrate diodes, resulting in unpredictable performance. Also, no pins should be taken below -0.3 V.

Calculate the junction temperature

Static Protection

All TPS2211A inputs and outputs contain ESD protection circuitry designed to withstand a 2-kV Human Body Model discharge as defined in MIL-STD-883C Method 3015. The AVCC and AVPP outputs can be exposed to potentially higher discharges from the external environment through the PC Card connector. Bypassing the output with a 0.1µF capacitor protects the device from discharges up to 10kv.

Note A: MOSFET switch S6 has a back gated diode from source to drain. Unused switch inputs must not be grounded.

Note B: The 16-pin DB package is shown in the figure.

Internal switch matrix, TPS2211A control logic

application information

The TPS6734 is a fixed 12-V output boost converter capable of outputting 120 mA from an input as low as 2.7 V. The device is compatible with the MAX734 regulator and offers the following benefits: lower supply current, wider operating input voltage range, and higher output current. As shown in Figure 1, the only external components required are: inductor, Schottky rectifier, output filter capacitor, input filter capacitor, and a small capacitor for loop compensation. When implemented using surface mount components, the entire converter occupies less than 0.7 inches of PCB space. An enable input is provided to shut down the converter and reduce supply current to 3µA when 12V is not required.

The TPS6734 is a 170 kHz current mode pulse width modulation (PWM) controller with an n-channel MOSFET power switch. The gate drive of the switch is derived from the 12 V output after startup to minimize the die area required to implement a 0.7Ω MOSFET and improve efficiency at input voltages below 5 V. Soft start is done by adding a small capacitor. A 1.22V reference (pin 2) is brought out for external use.

Note A: The enable terminal can be connected to the general purpose I/O terminal or high-order connections on the PCMCIA controller.

TPS2211A with TPS6734 12-V, 120mA power supply