LM3423MHBSTEVAL National Semiconductor, LM3423MHBSTEVAL Datasheet
LM3423MHBSTEVAL
Specifications of LM3423MHBSTEVAL
Related parts for LM3423MHBSTEVAL
LM3423MHBSTEVAL Summary of contents
Page 1
... The LM3421Q1/23Q1 are AEC-Q100 grade 1 qualified and LM3421Q0/23Q0 are AEC-Q100 grade 0 qualified. Typical Boost Application Circuit © 2010 National Semiconductor Corporation LM3421 LM3421Q1 LM3421Q0 LM3423 LM3423Q1 LM3423Q0 Features ■ ...
Page 2
Connection Diagrams Top View 16-Lead TSSOP EP NS Package Number MXA16A Ordering Information Order Number Spec. Package Type LM3421MH NOPB TSSOP-16 EP LM3421MHX NOPB TSSOP-16 EP LM3423MH NOPB TSSOP-20 EP LM3423MHX NOPB TSSOP-20 EP LM3421Q1MH NOPB TSSOP-16 EP LM3421Q1MHX NOPB ...
Page 3
Pin Descriptions LM3423 LM3421 Name COMP 4 4 CSH 5 5 RCT 6 6 AGND 7 7 OVP 8 8 nDIM 9 - FLT 10 - TIMR 11 - LRDY 12 ...
Page 4
... Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications EN, RPD, nDIM IN OVP, HSP, HSN, LRDY, FLT, DPOL RCT - continuous TIMR -100µA to +100µA Continuous COMP, CSH GATE, DDRV - continuous ...
Page 5
Symbol Parameter OV THRESHOLDS OVP OVP OVLO Threshold CB OVP OVP Hysteresis Source HYS Current DPOL THRESHOLDS DPOL DPOL Logic Threshold THRES H R DPOL Pullup Resistance DPOL FAULT TIMER V Fault Threshold FLTTH I Fault Pin Source Current FLT ...
Page 6
Symbol Parameter DIM DRIVER (DIM, DDRV) nDIM nDIM / UVLO Threshold VTH nDIM nDIM Hysteresis Current HYS R DDRV Sourcing Resistance SRC(DDRV) R DDRV Sinking Resistance SNK(DDRV) PULL-DOWN N-CHANNEL MosFETS R RPD Pull-down Resistance RPD R FLT Pull-down Resistance FLT ...
Page 7
Typical Performance Characteristics Boost Efficiency vs. Input Voltage V = 32V (9 LEDs) (Note O Boost LED Current vs. Input Voltage V = 32V (9 LEDs) (Note O Analog Dimming V = 21V (6 LEDs 24V O IN ...
Page 8
V vs. Junction Temperature CSH V vs. Junction Temperature RCT t vs. Junction Temperature ON-MIN www.national.com V vs. Junction Temperature CC 300673b0 V vs. Junction Temperature LIM 300673b2 300673b4 8 300673b1 300673b3 ...
Page 9
Block Diagram Theory of Operation The LM3421/23 are N-channel MosFET (NFET) controllers for buck, boost and buck-boost current regulators which are ideal for driving LED loads. The controller has wide input volt- age range allowing for regulation of a variety ...
Page 10
CURRENT REGULATORS Current regulators can be designed to accomplish three basic functions: buck, boost, and buck-boost. All three topologies in their most basic form contain a main switching MosFET, a recirculating diode, an inductor and capacitors. The LM3421/23 is designed ...
Page 11
SWITCHING FREQUENCY An external resistor (R ) connected between the RCT pin and T the switch node (where D1, Q1, and L1 connect), in combi- nation with a capacitor (C ) between the RCT and AGND pins, T sets the ...
Page 12
AVERAGE LED CURRENT The LM3421/23 uses an external current sense resistor (R ) placed in series with the LED load to convert the LED SNS current (I ) into a voltage ( shown in LED SNS HSP and ...
Page 13
CURRENT SENSE/CURRENT LIMIT The LM3421/23 achieves peak current mode control using a comparator that monitors the main MosFET (Q1) transistor current, comparing it with the COMP pin voltage as shown in Figure 6. Further, it incorporates a cycle-by-cycle over-current protection ...
Page 14
CONTROL LOOP COMPENSATION The LM3421/23 control loop is modeled like any current mode controller. Using a first order approximation, the uncompen- sated loop can be modeled as a single pole created by the output capacitor and, in the boost and ...
Page 15
To mitigate this problem, a compensator should be designed to give adequate phase margin (above 45°) at the crossover frequency. A simple compensator using a single capacitor at the COMP pin (C ) will add a dominant pole to the ...
Page 16
OVER-VOLTAGE LOCKOUT (OVLO) FIGURE 12. Over-Voltage Protection Circuitry The LM3421/23 can be configured to detect an output (or in- put) over-voltage condition via the OVP pin. The pin features a precision 1.24V threshold with 23 µA (typical) of hysteresis current ...
Page 17
PWM DIMMING The active low nDIM pin can be driven with a PWM signal which controls the main NFET and the dimming FET (dim- FET). The brightness of the LEDs can be varied by modulat- ing the duty cycle of ...
Page 18
FIGURE 18. Boost Level-Shifted PWM Circuit LM3423 ONLY: DPOL, FLT, TIMR, and LRDY The LM3423 has four additional pins: DPOL, FLT, TIMR, and LRDY. The DPOL pin is simply used to invert the DDRV po- larity . If DPOL is ...
Page 19
Design Considerations This section describes the application level considerations when designing with the LM3421/23. For corresponding cal- culations, refer to the Design Guide section. INDUCTOR The inductor (L1) is the main energy storage device in a switching regulator. Depending on ...
Page 20
MAIN MosFET / DIMMING MosFET The LM3421/23 requires an external NFET (Q1) as the main power MosFET for the switching regulator recommend have a voltage rating at least 15% higher than the maximum transistor voltage to ...
Page 21
Basic Topology Schematics BOOST REGULATOR (V < 30067322 www.national.com ...
Page 22
BUCK REGULATOR (V > www.national.com 22 30067351 ...
Page 23
BUCK-BOOST REGULATOR 23 30067350 www.national.com ...
Page 24
Design Guide Refer to Basic Topology Schematics section. SPECIFICATIONS Number of series LEDs: N Single LED forward voltage: V LED Single LED dynamic resistance: r LED Nominal input voltage Input voltage range IN-MAX IN-MIN Switching ...
Page 25
LED RIPPLE CURRENT Set the nominal LED ripple current (Δi LED-PP the output capacitance ( Buck Boost and Buck-boost To set the worst case LED ripple current, use D solving for C . Remember, when PWM dimming ...
Page 26
A high frequency compensation pole (ω attenuate switching noise and provide better gain margin. As- = 10Ω, C suming R is calculated according to the higher FS FS value of the pole and the RHP zero of the system (shown ...
Page 27
The current rating should be at least 10% higher than the maximum average diode current (I D-MAX Buck Boost and Buck-boost Replace D with D in the I equation to solve for the MAX D-MAX average diode current (I ). ...
Page 28
Design Example DESIGN #1 - LM3421 BUCK-BOOST Application SPECIFICATIONS 3.5V LED r = 325 mΩ LED V = 24V 10V IN-MIN V = 70V IN-MAX f = 500 kHz ...
Page 29
OPERATING POINT Solve for V and Solve for D, D and D : MAX MIN 2. SWITCHING FREQUENCY Assume and solve for The closest standard ...
Page 30
PEAK CURRENT LIMIT Solve for R : LIM The closest standard resistor is 0.04 Ω therefore I The chosen component from step 6 is: 7. LOOP COMPENSATION ω is approximated: P1 ω is approximated approximated: U0 ...
Page 31
The chosen component from step 10 is: 11. INPUT UVLO Solve for R : UV2 The closest standard resistor is 130 kΩ therefore V Solve for R : UV1 The closest standard resistor is 18.2 kΩ making V The chosen ...
Page 32
DESIGN #1 Bill of Materials Qty Part ID 1 LM3421 1 C BYP 1 C CMP ...
Page 33
Applications Information The following designs are provided as reference circuits. For a specific design, the steps in the Design Procedure section should be performed. In all designs filter (0.1 µF, 10Ω) is recommended at VIN placed as close ...
Page 34
DESIGN #2 Bill of Materials Qty Part ID 1 LM3421 1 C BYP 1 C CMP D1 Q1 ...
Page 35
DESIGN #3 - LM3421 BUCK-BOOST Application Features • Input: 10V to 30V • Output: 4 LEDs at 2A • PWM Dimming up to 10kHz • Analog Dimming • 600 kHz Switching Frequency 35 300673h6 www.national.com ...
Page 36
DESIGN #3 Bill of Materials Qty Part ID 1 LM3421 BYP CMP REF ...
Page 37
DESIGN #4 - LM3423 BOOST Application Features • Input: 18V to 38V • Output: 12 LEDs at 700mA • High Side PWM Dimming kHz • Analog Dimming • Zero Current Shutdown • 700 kHz Switching Frequency 37 ...
Page 38
DESIGN #4 Bill of Materials Qty Part ID 1 LM3423 1 C BYP 1 C CMP D1 ...
Page 39
DESIGN #5 - LM3421 BUCK-BOOST Application Features • Input: 10V to 70V • Output: 6 LEDs at 500mA • PWM Dimming kHz • Slow Fade Out • MosFET R Sensing DS-ON • 700 kHz Switching Frequency 39 ...
Page 40
DESIGN #5 Bill of Materials Qty Part ID 1 LM3421 BYP 1 C CMP ...
Page 41
DESIGN #6 - LM3423 BUCK Application Features • Input: 15V to 50V • Output: 3 LEDs at 1.25A • PWM Dimming kHz • LED Status Indicator • Zero Current Shutdown • 700 kHz Switching Frequency 41 300673h8 ...
Page 42
DESIGN #6 Bill of Materials Qty Part ID 1 LM3423 1 C BYP CMP DIM ...
Page 43
DESIGN #7 - LM3423 BUCK-BOOST Application Features • Input: 15V to 60V • Output: 8 LEDs at 2.5A • Fault Input Disconnect • Zero Current Shutdown • 500 kHz Switching Frequency 43 300673i0 www.national.com ...
Page 44
DESIGN #7 Bill of Materials Qty Part ID 1 LM3423 1 C BYP 1 C CMP TMR ...
Page 45
DESIGN #8 - LM3421 SEPIC Application Features • Input 36V • Output: 5 LEDs at 750mA • PWM Dimming kHz • 500 kHz Switching Frequency 45 300673i8 www.national.com ...
Page 46
DESIGN #8 Bill of Materials Qty Part ID 1 LM3421 1 C BYP 1 C CMP SEP L1 ...
Page 47
Physical Dimensions inches (millimeters) unless otherwise noted For Ordering, Refer to Ordering Information Table For Ordering, Refer to Ordering Information Table TSSOP-16 Pin EP Package (MXA) NS Package Number MXA16A TSSOP-20 Pin EP Package (MXA) NS Package Number MXA20A 47 ...
Page 48
... For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Amplifiers www.national.com/amplifiers Audio www.national.com/audio Clock and Timing www.national.com/timing Data Converters www.national.com/adc Interface www.national.com/interface LVDS www.national.com/lvds Power Management www.national.com/power Switching Regulators www.national.com/switchers LDOs www.national.com/ldo LED Lighting www ...