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LED DRIVER. IS31LT3948 Datasheet

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LED DRIVER. IS31LT3948 Datasheet






IS31LT3948 DRIVER. Datasheet pdf. Equivalent




IS31LT3948 DRIVER. Datasheet pdf. Equivalent





Part

IS31LT3948

Description

PFM MODE BOOST LED DRIVER



Feature


IS31LT3948 PFM MODE BOOST LED DRIVER WIT H THE EXTERNAL NMOS OCTOBER 2011 GENERA L DESCRIPTION The IS31LT3948 is a PFM s tep-up DC-DC converter designed for dri ving the white LED arrays for large siz e LCD panel backlighting applications. It can deliver stable constant output c urrent from a few milliamps up to 2A, p rogrammed via an external resistor. The IS31LT3948 utiliz.
Manufacture

ISSI

Datasheet
Download IS31LT3948 Datasheet


ISSI IS31LT3948

IS31LT3948; es a control scheme in which the output is automatically adjusted to the optimu m output voltage for the system, maximi zing the efficiency. Furthermore, the c ontrol scheme is inherently stable remo ving the need to provide additional loo p compensation. The device features ext ernal PWM dimming, which allows the fle xible control of the back-lighting lumi nance. The IS31LT3.


ISSI IS31LT3948

948 has a wide input voltage range from 5V to 100V (Note). An integrated OVP ci rcuit protects the chip and the system even under no-load conditions. Note: Th e IS31LT3948 has an internal 5V shunt r egulator connected to the VCC pin. A dr opping resistor must be connected betwe en the VCC pin and VIN to limit current flow. VIN voltages above 100V are allo wed but care must .


ISSI IS31LT3948

be taken to ensure that the output volta ge remains greater than VIN, and that t he NMOS voltage rating is sufficiently large. FEATURES • • • • • • Wide input voltage range: 5V-100V Constant Current Output limited only b y external component selection (Note) N o loop compensation required Internal o ver-voltage protection Internal over-te mperature protection Operating t.

Part

IS31LT3948

Description

PFM MODE BOOST LED DRIVER



Feature


IS31LT3948 PFM MODE BOOST LED DRIVER WIT H THE EXTERNAL NMOS OCTOBER 2011 GENERA L DESCRIPTION The IS31LT3948 is a PFM s tep-up DC-DC converter designed for dri ving the white LED arrays for large siz e LCD panel backlighting applications. It can deliver stable constant output c urrent from a few milliamps up to 2A, p rogrammed via an external resistor. The IS31LT3948 utiliz.
Manufacture

ISSI

Datasheet
Download IS31LT3948 Datasheet




 IS31LT3948
IS31LT3948
PFM MODE BOOST LED DRIVER WITH THE EXTERNAL NMOS
GENERAL DESCRIPTION
FEATURES
OCTOBER 2011
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.
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.
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
SOP-8 package
Note: The maximum output current is determined by Vout/Vin ratio
as well as the external components. If output current and Vout/Vin
ratio is high, high current components of inductor and NMOS are
needed.
APPLICATIONS
TV Monitor Backlighting,
Notebook
Automotive
Street Lamp
LED Lighting
http://www.DataSheet4U.net/
TYPICAL OPERATING CIRCUIT
VIN(5~100V)
L1
D1
LED(+)
R1
C1
R2
C2
VCC
TOFF
ADJ
GND
GATE
CS
OVP
FB
M1
C3
R3
R4
R5
LED(-)
Rfb
Figure 1 Typical Operating Circuit
Copyright © 2011 Integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products at any time
without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are advised
to obtain the latest version of this device specification before relying on any published information and before placing orders for products.
Integrated Silicon Solution, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the
product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not
authorized for use in such applications unless Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that:
a.) the risk of injury or damage has been minimized;
b.) the user assume all such risks; and
c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 8/31/2011
1
datasheet pdf - http://www.DataSheet4U.net/




 IS31LT3948
IS31LT3948
PIN CONFIGURATIONS
Package
SOP-8
VCC
Top View
18
OVP
TOFF
ADJ
2
3
7 FB
6 CS
GND 4
5 GATE
PIN DESCRIPTIONS
Pin Name
1 VCC
2 TOFF
3 ADJ
4 GND
5 GATE
6 CS
7 FB
8 OVP
Function
Positive power supply input pin. Internally clamped at 5V (typical).
Off time setting pin. An external resistor connected to this PIN forms an
RC discharge path to generate a constant minimum off time of the NMOS
Enable and input peak current control pin. Pulled up to 4.5V internally to
set VCSTH =0.24V when ADJ is floating. If VADJ<0.5V, NMOS will always
shutdown. If 0.5• VADJ• 2.4V, VCSTH = VADJ/10. If VADJ>2.4V, VCSTH =0.24V
Ground
Driver’s output for the gate of the external NMOS
Current sense input for the boost, peak current control loop
Feedback voltage input pin. Used to regulate the current of LEDs by
keeping VFB=0.3V.
Overvoltage protection input pin.,http://www.DataSheet4U.net/ if the voltage of OVP exceed 1V, Gate
will always shutdown
ORDERING INFORMATION
Order Part No.
Package
IS31LT3948-GRLS2-TR SOP-8, Lead-free
QTY/Reel
2500
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 8/31/2011
2
datasheet pdf - http://www.DataSheet4U.net/




 IS31LT3948
IS31LT3948
ABSOLUTE MAXIMUM RATINGS
Parameter
Value
VCC to GND
-0.3V to 6V
CS, ADJ,GATE,TOFF,OVP,FB
-0.3V to 6V
VCC Max. Input Current(note)
Junction Temperature Range
Storage Temperature Range
10mA
-40oC to +150oC
-65oC to +150oC
ESD Human Model
3500V
Notes:
1. Exceeding VCC maximum input current may cause the pin not to clamp at 5V.
2. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings
only and functional operation of the device at these or any other condition beyond those indicated in the operational sections of the
specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, Vin=10V, Rin=10K, ADJ floating, Tamb=25 oC)
Symbol
Parameter
Conditions
VINDC Input voltage
VCC
UVLO
VCC clamp voltage
Undervoltage threshold
Δ UVLO Undervoltage threshold hysteresis
Supply voltage
connected to VCC via a
appropriate resistor
(Note)
Rin=10KOhm
VCC rising
http://www.DataSheet4U.net/
Min
5
4.3
2.0
spec
Typ
Max
Unit
100 V
5 5.6 V
2.7 3.0 V
300 mV
ISS
VCSTH
Quiescent supply current
Quiescent supply current when
VCC undervoltage
Peak current sense threshold
VCC=5V
VCC=2.5V
ADJ=5V
250
50
215 240
400 uA
75 uA
265 mV
TBLANK Peak current sense blank interval VCS=VCSTH+50mV
500 ns
TOFF Fixed turn-off interval
Rext=250KΩ
10 us
Peak current control low threshold
VADJ
Peak current control high threshold
0.5 V
2.4 V
TSD
TSD-HYS
Thermal shutdown threshold
Thermal shutdown hysteresis
125 oC
20 oC
VfbTH Feedback voltage threshold
0.29
0.3
0.31
V
VOVP-TH Overvoltage input threshold
0.9 1
1.1 V
Note:
VIN is the input voltage. When VIN • 5V, connect input voltage directly to Vcc. When VIN > 5V, input voltage should be connected to Vcc pin via
an appropriately valued resistor.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 8/31/2011
3
datasheet pdf - http://www.DataSheet4U.net/



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