The LM3559 is a 2-MHz fixed-frequency synchronous boost converter with two 900-mA constant current drivers for high-current white LEDs. The dual high-side current sources allow for grounded cathode LED operation and can be tied together for providing flash currents of up to 1.8 A. An adaptive regulation method ensures the current for each LED remains in regulation and maximizes efficiency.
The LM3559 is controlled via an I2C-compatible interface. Features include: an internal 4-bit ADC to monitor the LED voltage, independent LED current control, a hardware flash enable allowing a logic input to trigger the flash pulse, dual TX inputs which force the flash pulse into a low-current torch mode allowing for synchronization to RF power amplifier events or other high-current conditions, an integrated comparator designed to monitor an NTC thermistor and provide an interrupt to the LED current, an input voltage monitor to monitor low battery conditions, and a flash current scale-back feature that actively monitors the battery voltage and optimizes the flash current during low battery-voltage conditions. Additionally, an active high HWEN input provides a hardware shutdown during system software failures.
The 2-MHz switching frequency, overvoltage protection, and adjustable current limit allow for the use of tiny, low-profile (1-µH or 2.2-µH) inductors and (10-µF) ceramic capacitors. The device is available in a ultra-small 16-pin DSBGA package (total solution size < 26 mm2) and operates over the –40°C to +85°C temperature range.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM3559 | DSBGA (16) | 1.96 mm × 1.96 mm |
Changes from A Revision (May 2013) to B Revision
Changes from * Revision (May 2013) to A Revision
PIN | TYPE | DESCRIPTION | |
---|---|---|---|
NO. | NAME | ||
A1 | LED1 | Power | High-side current source output for flash LED1 |
A2, B2 | OUT | Power | Step-up DC-DC converter output. Connect a 10-µF ceramic capacitor between this pin and GND. |
A3, B3 | SW | Power | Drain connection for internal NMOS and synchronous PMOS switches |
A4, B4 | GND | Ground | Ground |
B1 | LED2 | Output | High-side current source output for flash LED2 |
C1 | LEDI/NTC | Input/Output | Configureable as a high-side current source output for indicator LED or comparator input for LED temperature sensing |
C2 | TX1/TORCH/GPIO1 | Input/Output | Configureable as a dual-polarity RF power amplifier synchronization input, a hardware torch mode enable, or as a general purpose logic I/O. This pin has an internal 300-kΩ pulldown to GND. |
C3 | STROBE | Input | Active high hardware flash enable. Drive STROBE high to turn on the flash current pulse. This pin has an internal 300-kΩ pulldown to GND. |
C4 | IN | Power | Input voltage connection. Connect IN to the input supply, and bypass to GND with a minimum 10-µF or larger ceramic capacitor. |
D1 | TX2/INT/GPIO2 | Input/Output | Configurable as a dual-polarity power amplifier synchronization input, an interrupt output, or as a general purpose logic I/O. This pin has an internal 300-kΩ pulldown to GND. |
D2 | SDA | Input/Output | Serial data input output. High impedance in shutdown or in power down. |
D3 | SCL | Input | Serial clock input. High impedance in shutdown or in power down. |
D4 | HWEN | Input | Logic high hardware enable. HWEN is a high impedance input and is normally connected with an external pullup resistor to a logic high voltage. |