LM3570

If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
VIN pin: Voltage to GND .............................................-0.3V to 6.0V
EN, PWM: Voltage to GND........... -0.3V to (V_IN +0.3V) w/ 6.0V max
Continuous Power Dissipation
(Note 3)................................................................Internally Limited
Junction Temperature (T_J-MAX) ...............................................150
Storage Temperature Range ...................................-65to +150
Maximum Lead Temperature
(Soldering, 10 sec.)............................................................(Note 4)
ESD Rating(Note 5)
Human Body Model.................................................................2.0KV
Machine Model.......................................................................200KV

The LM3570 device provides a complete LED driver solution for wireless handsets and other portable devices using a
display and keypad. With three constant current sources, up to three white LEDs can be used for display lighting with
excellent current matching (0.3% typ.). The regulated 4.35V output voltage is perfect for driving auxiliary keypad LEDs in voltage mode.

The LM3570 utilizes a high efficiency 3/2 CMOS chargepump with a pre-regulation loop that minimizes conducted noise on the input. It accepts an input voltage range from 2.7V to 5.5V and maintains a constant current determined by the current through an external R_SET resistor.

The device supplies up to 80mA of total load current to accommodate any combination of up to three white LEDs,and additional current from V_OUT. The switching frequency is set at 500kHz. (typ.) to keep the conducted noise spectrum
away from sensitive frequencies within portable RF devices.

By applying a pulse width modulated (PWM) signal to the PWM pin, the user has the ability to independently control the brightness of the regulated current source outputs without shutting down the regulated output voltage.