Analog Devices Inc./Maxim Integrated

The MAX16840 is an LED driver IC for lighting applications. It includes all the necessary features to design low-component-count LED drivers for 12V AC and 24V AC input (e.g., MR16) light bulbs. A proprietary input-current control scheme allows LED lamps based on this device to be compatible with electronic transformers, and dimmable with standard trailing-edge dimmers (where electronic transformers are present).The IC can be used in buck, boost, and buck-boost topologies and features. It has an integrated 0.2Ω (max), 48V switching MOSFET.The IC uses constant-frequency average current-mode control. It senses the input current through the voltage at the FB pin, and regulates its average. An input pin (REFI) allows the setting of the input-current level. When the voltage at this pin is set below a certain threshold, the input current is proportional to this voltage, while when that voltage is beyond the threshold, the input current is set at a fixed, predefined level. This nonlinear behavior of REFI allows its use to achieve thermal foldback, by connecting it to an NTC resistor.The IC also features an internal overvoltage protection on the IN pin to protect the internal switching MOSFET from damage if the LED string is open or if the voltage on the LED string is too high.The IC has a separate EXT pin that can be used to guarantee that there is a kick-start of current at turn-on for low-input voltages for proper operation with electronic transformers. EXT drives an external npn transistor. Once the UVLO threshold of 5.5V is crossed on IN, EXT is pulled to ground and the external npn transistor is turned off.The IC is available in a 3mm x 3mm, 10-pin TDFN power package, and is rated over the -40°C to +125°C operating temperature range.ApplicationsMR16 and Other 12V AC or DC Input LED Lighting Applications

The MAX1684/MAX1685 are high-efficiency, internal-switch, pulse-width modulation (PWM) step-down switching regulators intended to power cellular phones, communicating PDAs, and handy-terminals. These devices deliver a guaranteed 1A output current from two lithium-ion (Li+) batteries. Their wide-input voltage range of 2.7V to 14V gives design flexibility and allows batteries to charge from a wall cube, since the ICs operate at the higher voltages that occur when the battery is removed. The output voltage is preset to 3.3V or can be externally adjusted from 1.25V to VIN.The low on-resistance power switch and built-in synchronous rectifier provide high efficiencies of up to 96%. There are four modes of operation: fixed-frequency, normal, low-power, and shutdown. The fixed-frequency PWM mode of operation offers excellent noise characteristics. The normal mode maintains high efficiency at all loads. The low-power mode is used to conserve power in standby or when full load is not required. The shutdown mode is used to power down the device for minimal current draw.The MAX1684 runs at 300kHz for applications that require highest efficiency. The MAX1685 runs at 600kHz to allow the use of smaller external components. These devices can also be synchronized to an external clock. Other features include a 100% duty cycle for low-dropout applications, an auxiliary 3V/5mA output, and a 1% accurate reference.Both devices are available in a space-saving 16-QSOP package. An evaluation kit is also available to help speed designs. For a similar device in a 10-pin µMAX® package with lower input voltage requirements (5.5V max), refer to the MAX1692 data sheet.ApplicationsCell PhonesComputer PeripheralsPDAs and Handy-TerminalsPersonal CommunicatorsTwo-Way Radios and Walkie-Talkies

The MAX1686 provides power for dual-voltage subscriber ID module (SIM) cards in portable applications such as GSM cellular phones. Designed to reside in the portable unit (cellular phone handset), the 1MHz charge pump converts a 2.7V to 4.2V input to regulated 5V output. The MAX1686H has a nominal output voltage of 5.0V, while the MAX1686 is set to 4.75V to reduce SIM card current drain. The charge pump has only 45µA quiescent supply current, which reduces to 3µA when a 3V-capable SIM card is being powered and the charge pump is disabled. An internal input/output shorting switch provides power for 3V SIM cards.The MAX1686/MAX1686H require only three external capacitors around their space-saving, thin (1mm) 8-pin µMAX® packages.ApplicationsGSM Cellular PhonesPCS PhonesPersonal CommunicatorsPortable POS Terminals

The MAX1687/MAX1688 step-up DC-DC converters deliver up to 2W from a single Li-Ion or three NiMH cells. The devices are ideal for burst-load applications such as GSM cell phones and wireless LANs, where the RF power amplifiers require short, high current bursts. The MAX1687/MAX1688 reduce battery surge current by slowly charging a reservoir capacitor, which supplies the necessary peak energy for the load current burst. As a result, the peak battery current is limited, thus maximizing battery life and minimizing battery voltage sag and transient dips.An internal synchronous rectifier provides over 90% conversion efficiency and eliminates the need for an external Schottky diode. A logic shutdown mode reduces the shutdown current to only 3µA. The devices can be disabled during current bursts (RF transmit mode) to eliminate switching noise.The switching frequency of the MAX1687/MAX1688, controlled by the selected inductor, can exceed 1MHz. Two external resistors set the output voltage from 1.25V to 6V. The MAX1687 controls peak battery current, while the MAX1688 features a more advanced, adaptive constant-recharge-time algorithm that maximizes battery life. The MAX1687/MAX1688 are available in thin 16-pin TSSOP (1.1mm max height) or standard 8-pin SO packages.ApplicationsGSM PhonesPC Cards (PCMCIA)Wireless Handsets

The MAX16895—MAX16899 is a family of small, low power, voltage-monitoring circuits with sequencing capability. These miniature devices offer tremendous flexibility with an adjustable threshold capable of monitoring down to 0.5V and an external capacitor-adjustable time delay. These devices are ideal for use in power-supply sequencing, reset sequencing, and power-switching applications. Multiple devices can be cascaded for complex sequencing applications.A high-impedance input with a 0.5V threshold allows an external resistive divider to set the monitored threshold. The output asserts (OUT = high or active-low OUT) when the input voltage rises above the 0.5V threshold and the enable input is asserted (ENABLE = high or active-low ENABLE = low). When the voltage at the input falls below 0.5V or when the enable input is deasserted (ENABLE = low or active-low ENABLE = high), the output deasserts (OUT = low or active-low OUT = high). All devices provide a capacitor-programmable delay time from when the input rises above 0.5V to when the output is asserted. The MAX1689_A versions provide the same capacitor-adjustable delay from when enable is asserted to when the output asserts. The MAX1689_P devices have a 150ns propagation delay from when enable is asserted to when the output asserts.The MAX16895A/P offers an active-high enable input and an active-high push-pull output. The MAX16896A/P offers an active-low enable input and an active-low pushpull output. The MAX16897A/P offers an active high enable input and an active-high open-drain output. Finally, the MAX16898A/P offers an active-low enable input and an active-low open-drain output. The MAX16899A/P offers an active-low enable with an active high push-pull output.All devices operate from a 1.5V to 5.5V supply voltage and are fully specified over the -40°C to +125°C operating temperature range. These devices are available in ultra-small 6-pin μDFN (1.0mm x 1.5mm) and thin SOT23 (1.60mm x 2.90mm) packages.ApplicationsMedical EquipmentIntelligent InstrumentsPortable EquipmentComputers/ServersCritical µP MonitoringSet-Top BoxesTelecom