IS31LT3948-GRLS2-TR ISSI, IS31LT3948-GRLS2-TR Datasheet
![no-image](/images/no-image-200.jpg)
IS31LT3948-GRLS2-TR
Specifications of IS31LT3948-GRLS2-TR
Related parts for IS31LT3948-GRLS2-TR
IS31LT3948-GRLS2-TR Summary of contents
Page 1
... 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 ...
Page 2
... FB 8 OVP Ordering Information Order Part No. Package IS31LT3948-GRLS2-TR SOP-8, Lead-free Integrated Silicon Solution, Inc. – www.issi.com Rev.B, 12/24/2012 Top View 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 ...
Page 3
... IS31LT3948 Absolute Maximum Ratings VCC to GND CS, ADJ,GATE,TOFF,OVP,FB VCC Max. Input Current(note) Junction Temperature Range Storage Temperature Range ESD Human Model Note: Exceeding VCC maximum input current may cause the pin not to clamp at 5V. 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 ...
Page 4
... IS31LT3948 Typical Performance Characteristics 400 380 360 340 320 , Vout=40V,Rfb=0.825 Rcs=0.12 L=100uH,Cout=220uF(Low ESR) 300 Vin(V) Figure 2. Vin & Iout 400 380 360 340 320 Vin=12V,Rfb=0.825,Rcs=0.12 ESR) L=100uH,Cout=220uF(Low 300 Vout(V Figure 4. Vout & Iout ...
Page 5
... IS31LT3948 800 770 740 710 680 Vout=48V,Rfb=0.392,Rcs=0.1 Vint=24V,Rfb=0.392,Rcs=0.1 ESR) ESR) L=100uH,Cout=220uF(Low L=100uH,Cout=220uF(Low 650 Vout(V) Figure 8. Vout & Iout Integrated Silicon Solution, Inc. – www.issi.com Rev.B, 12/24/2012 100 Vin=24V,Rfb=0.392 ...
Page 6
... When the PWM input is high (V IS31LT3948 operates normally to regulate the output current. When PWM is low logic (V and IS31LT3948 is shutdown. Using a fixed frequency PWM signal and changing the duty cycle adjusts the average output current. The recommended 5V PWM frequency is between 200Hz and 1KHz recommended to use AP2306 ...
Page 7
... CSTH CSTH Integrated Silicon Solution, Inc. – www.issi.com Rev.B, 12/24/2012 Input Capacitor The input capacitor of the IS31LT3948 will supply the transient input current of the power inductor. Value of 100μF or higher is recommended to prevent excessive input voltage ripple. Setting T IS31LT3948 operates in a pulsed frequency modulation mode ...
Page 8
... Proportionally lower ripple can be achieved with higher capacitor values. Schottky Rectifier The external diode for the IS31LT3948 must be a Schottky diode, with low forward voltage drop and fast switching speed. The diode’s average current rating must exceed the application’s average output current. ...
Page 9
... IS31LT3948 VIN(5~100V PWM Integrated Silicon Solution, Inc. – www.issi.com Rev.B, 12/24/2012 L1 M1 VCC GATE TOFF CS ADJ OVP R3 GND FB Figure.12 External NMOS PWM dimming Figure.13 RC filter PWM dimming D1 LED(+) R4 LED(-) Rfb 9 ...
Page 10
... IS31LT3948 Example Input: Vin = 12~24V Output: Iout = 350mA, Vout≈30~40V (9~12LEDs, Vf=3.3V) To calculate the worst case parameter, use the minimum input voltage, the maximum output voltage, and maximum output current. So choose: Vin = 12V, Iout = 350mA, Vout≈40V (12LEDs, Vf=3.3V and C1&C2 Assume Iin = 2.5mA ...
Page 11
... IS31LT3948 6. R4 set OVP Set V = Vout+5V = 45V OVP OVP OVP Choose R5=10kΩ, then R4 = 470kΩ. 7. NMOS M1 and diode D1 I1 >I (NMOS) peak IN ( ) V1 >V (NMOS) OVP Integrated Silicon Solution, Inc. – www.issi.com Rev ...
Page 12
... IS31LT3948 Classification Reflow Profiles Preheat & Soak Temperature min (Tsmin) Temperature max (Tsmax) Time (Tsmin to Tsmax) (ts) Average ramp-up rate (Tsmax to Tp) Liquidous temperature (TL) Time at liquidous (tL) Peak package body temperature (Tp)* Time (tp)** within 5°C of the specified classification temperature (Tc) Average ramp-down rate (Tp to Tsmax) Time 25° ...
Page 13
... IS31LT3948 Tape and Reel Information Integrated Silicon Solution, Inc. – www.issi.com Rev.B, 12/24/2012 13 ...
Page 14
... IS31LT3948 Package Information Integrated Silicon Solution, Inc. – www.issi.com Rev.B, 12/24/2012 14 ...