2.5-V Power management for DSP systems

Low-power 500-mA low dropout regulator for 2.5-V systems

Product Features

Fixed 2.5-V output at 0 to 500 mA
VDO = 95 mV max at 100 mA
IQ = 292 µA
Shutdown mode: 0.5 µA max
±2% output tolerance
Characterized for operation from 0°C to 125°C

The TPS71025 offers designers an order of magnitude reduction in dropout voltage and quiescent current over conventional bipolar Low Dropout (LDO) Voltage Regulators. The latest member of the family of PMOS LDOs provides reduced power consumption and longer battery life in handheld and portable battery powered systems such as PDAs, palmtops, cellphones and other systems utilizing the emerging 2.5-V logic functions.

The TPS71025 uses a voltage controlled PMOS pass transistor. In contrast, bipolar regulators use a PnP pass element, the base current of which is directly proportional to the load current through the regulator. The PMOS pass transistor results in very low quiescent currents (typically 292 µA) that remain virtually constant over the regulator’s full specified 500-mA output load. This pass transistor also acts as a low value resistor, less than 1 , so the dropout voltage is extremely low when compared to conventional bipolar LDOs. Typical dropout voltage under a 100-mA load, for instance, is a mere 95 mV maximum.

The TPS71025’s 2.5-V output is regulated to ±2% voltage tolerance over the full specified range for line, load and temperature changes. For additional power savings, a TTL logic-enabled standby mode reduces power consumption to 0.5 µA maximum. This addresses a critical requirement to extend battery life in power sensitive applications. This device is available in the ultra-thin TSSOP package for space sensitive applications.

The TPS71025 is available in 20-pin TSSOP, 8-pin SOIC and 8-pin DIP.

Industry's first 2.5-V supply voltage supervisor operates on 16 µA

Product Features

2.5-V supervisor
Preset 2.25-V reset threshold
I_CC = 16 µA (max)
No external pull-up or pull-down resistors
Characterized for operation from –40°C to 125°C

The TLC7725 is the industry’s first supply voltage supervisor available for 2.5-V systems and consumes only 16 µA of supply current. This device gives designers precision control of their 2.5-V power supply lines for low voltage DSPs and microprocessors. Additionally, component space and board count are reduced by the use of totem pole outputs that eliminate external pull-up or pull-down resistors. Along with battery-saving micropower operation, the TLC7725 also adds static memory backup functionality to the supervisor. These device features are extremely beneficial in laptops, cellphones and a variety of other battery-powered systems designed to utilize the newer 2.5-V digital functions.

The TLC7725 has a 2.25-V sense-voltage threshold. To eliminate undefined states during power-up, the /RESET output is guaranteed asserted when VDD reach 1 V; both outputs are defined once VDD reaches 2 V. Reset delay time is programmable and is set by an external timing capacitor. The TLC7725 also features functionality for controlling static memory chips with battery backup during power failure. The CONTROL pin, when driven by the memory select pin of a microprocessor, programs the RESET output to drive the chip select (CS) of the memory circuit.

The TLC7725 is the latest member in TI’s expanding family of LinBiCMOS™ supply voltage supervisors. Other options include 5 V, 3.3 V 3.0 V and adjustable. This family of supply line supervisors is available in the miniaturized 8-pin TSSOP package, further reducing board space requirements. Other package options are 8-pin SOIC and plastic DIP.

TI&&ME

Vol 25 January, 1998