Analog Devices Inc./Maxim Integrated

The MAX1553/MAX1554 drive white LEDs in series with a constant current to provide efficient display backlighting in cellular phones, PDAs, and other hand-held devices. The step-up converter includes an internal 40V, low RDSON, N-channel MOSFET switch for high efficiency and maximum battery life. The MAX1553 has a current limit of 480mA for driving two to six white LEDs, while the MAX1554 has a current limit of 970mA for driving up to 10 white LEDs.A single analog/PWM Dual Mode™ input provides two simple means of brightness adjustment. A separate enable input provides on/off control. Soft-start minimizes inrush current during startup.The MAX1553/MAX1554 are available in space-saving 8-pin TDFN 3mm x 3mm packages.ApplicationsCell PhonesColor Display BacklightPDA, Palmtop, and Wireless Handhelds

The MAX1551 and MAX1555 charge a single-cell lithium-ion (Li+) battery from both USB and AC adapter sources. They operate with no external FETs or diodes, and accept operating input voltages up to 7V.On-chip thermal limiting simplifies PC board layout and allows optimum charging rate without the thermal limits imposed by worst-case battery and input voltage. When the MAX1551 and MAX1555 thermal limits are reached, the chargers do not shut down, but progressively reduce charging current.The MAX1551 includes an active-low POK output to indicate when input power is present. If either charging source is active, active-low POK goes low. The MAX1555 instead features a active-low CHG output to indicate charging status.With USB connected, but without DC power, charge current is set to 100mA (max). This allows charging from both powered and unpowered USB hubs with no port communication required. When DC power is connected, charging current is set at 280mA (typ). No input-blocking diodes are required to prevent battery drain.The MAX1551 and MAX1555 are available in 5-pin thin SOT23 packages and operate over a -40°C to +85°C range.ApplicationsCell PhonesDigital CamerasPDAsWireless Appliances

The MAX1556/MAX1556A/MAX1557 are low-operating-current (16µA), fixed-frequency step-down regulators. High efficiency, low-quiescent operating current, low dropout, and minimal (27µA) quiescent current in dropout make these converters ideal for powering portable devices from 1-cell Li-ion or 3-cell alkaline/NiMH batteries. The MAX1556 delivers up to 1.2A; has pin-selectable 1.8V, 2.5V, and 3.3V outputs; and is also adjustable. The MAX1557 delivers up to 600mA; has pin-selectable 1V, 1.3V, and 1.5V outputs; and is also adjustable.The MAX1556/MAX1556A/MAX1557 contain a low-on-resistance internal MOSFET switch and synchronous rectifier to maximize efficiency and dropout performance while minimizing external component count. A proprietary topology offers the benefits of a high fixed-frequency operation while still providing excellent efficiency at both light and full loads. A 1MHz PWM switching frequency keeps components small. Both devices also feature an adjustable soft-start to minimize battery transient loading.The MAX1556/MAX1556A/MAX1557 are available in a tiny 10-pin TDFN (3mm x 3mm) package.ApplicationsCell Phones/SmartphonesDigital Cameras and CamcordersHandheld InstrumentsPDAs and Palmtop ComputersPortable MP3 and DVD Players

The MAX1558/MAX1558H are dual, current-limited switches with autoreset for USB applications. Autoreset latches the switch off if it is shorted for more than 20ms, saving system power. The shorted output is then tested to determine when the short is removed to automatically restart the channel. Each channel delivers up to 1.2A and meets all IEC specifications for USB ports. Low quiescent supply current (45µA) and standby current (3µA) conserve battery power in portable applications.The MAX1558/MAX1558H safety features ensure that the USB port is protected. Built-in thermal-overload protection limits power dissipation and junction temperature. Accurate, programmable current-limiting circuitry protects the input supply against both overload and short-circuit conditions. 20ms fault blanking enables the circuit to ignore transient faults, such as those caused when hot swapping a capacitive load, preventing false alarms to the host system. The MAX1558/MAX1558H also feature reverse-current protection circuitry to block current flow from the output to the input when the switches are off.The MAX1558/MAX1558H are available in space-saving 3mm x 3mm, 10-pin TDFN packages. The MAX1558 is enabled with an active-low signal, and the MAX1558H is enabled with an active-high signal.ApplicationsDocking StationsNotebook Computers and DesktopsPDAs and Palmtop ComputersUSB Ports and Hubs