IS31LT3948-GRLS2 Datasheet, PDF (1/18 Pages) Integrated Silicon Solution, Inc – PFM MODE BOOST LED DRIVER WITH THE EXTERNAL NMOS

IS31LT3948
PFM MODE BOOST LED DRIVER WITH THE EXTERNAL NMOS
GENERAL DESCRIPTION
The IS31LT3948 is a PFM step-up DC-DC converter
designed for driving the white LED arrays for large
size LCD panel backlighting applications. It can
deliver stable constant output current from a few
milliamps up to 2A, programmed via an external
resistor.
The IS31LT3948 utilizes a control scheme in which
the output is automatically adjusted to the optimum
output voltage for the system, maximizing the
efficiency. Furthermore, the control scheme is
inherently stable removing the need to provide
additional loop compensation.
The device features external PWM dimming, which
allows the flexible control of the back-lighting
luminance.
The IS31LT3948 has a wide input voltage range
from 5V to 100V (Note). An integrated OVP circuit
protects the chip and the system even under no-load
conditions.
The chip is assembled in SOP-8 package. It
operates from 5V to 100V over two temperature
ranges of -40°C to +85°C and -40°C to +125°C.
Note: The IS31LT3948 has an internal 5V shunt
regulator connected to the VCC pin. A dropping
resistor must be connected between the VCC pin
and VIN to limit current flow. VIN voltages above
100V are allowed but care must be taken to ensure
that the output voltage remains greater than VIN,
and that the NMOS voltage rating is sufficiently
large.
FEATURES
February 2015
 Wide input voltage range: 5V~100V
 Constant current output limited only by external
component selection (Note)
 No loop compensation required
 Internal over-voltage protection
 Internal over-temperature protection
 Operating temperature range -40C to +85C
(IS31LT3948-GRLS2-TR)
 Operating temperature range -40C to +125C
(IS31LT3948-GRLS4-TR)
 SOP-8 package
Note: The maximum output current is determined by
V_OUT/V_IN ratio as well as the external components. If
output current and V_OUT/V_IN ratio is high, high current
components of inductor and NMOS are needed.
APPLICATIONS
 TV monitor backlighting
 Notebook
 Automotive
 Street lamp
 LED lighting
TYPICAL APPLICATION CIRCUIT
Figure 1 Typical Application Circuit
Integrated Silicon Solution, Inc. – www.issi.com
1
Rev. D, 01/21/2015