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Document overview
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Technical content
Features
Linear Balance Control for 4-Channel LED Arrays Wide LED String Voltage Range: 100V Wide VCC Voltage: 10.5V to 35V External Linear Regulation Switch: MOSFET or BJT Internal Voltage Regulator for Feedback Monitoring Drain-Source Voltage of External Switch Precision Current Accuracy Trimmed to 1.5% Supports External PWM Dimming - Positive Supports Wide Dimming Ratio: 0.5%~100% Adaptive Linear Regulation Method Generate Integrated Feedback Signal for Primary Controller (Current Feedback + PWM Dimming) High Efficiency by Primary Side Direct Feedback Thermal Shutdown (Auto-Recovery) Over-Voltage Regulation Channel Individual Open-LED Protection Channel Individual Short-LED Protection Channel Individual Over-Current Protection Error Flag Output 28-Pin SOIC
Applications
LED BLU for LCD TV LED BLU for LCD Monitor LED Lighting
Description
The FAN7346 is an LED current-balance controller that controls 4-LED arrays to maintain equal LED current. The FAN7346 has a high withstanding voltage, so is suitable for edge-type LED BLU and LED Lighting. To minimize components between primary to secondary, the FAN7346 generates a new integrated feedback signal. The FAN7346 provides various protections, such as over-voltage regulation, open-LED protection, thermal protection, and drain-sour ce voltage protection of regulating switch (the FAN7346 monitors all LED arrays drain-source voltage for prot ection). To increase system reliability, FAN7346 applies individual string protection. Because FAN7346 integrates so many functions it reduces overall BOM costs. LED brightness can be linearly varied up to LED current by applying an external Pulse Width Modulated (PWM) signal to the PWM pin. The FAN7346 is available in a 28-SOIC package.
Ordering Information
Temperature Package Packing Method FAN7346M -40 to +125°C 28-Lead, Small-Out line Integrated Circuit (SOIC) Rail FAN7346MX Tape & Reel
Figure 1. Internal Block Diagram
Figure 2. Package Diagram 1 OVR This pin is input for over-voltage regulation. pin is externally connected to the cathode of the feedback photo-coupler. 3 CMP This pin is for compensation of the minimum channel voltage feedback. must be tied together. In single operation, this pin must be open. 5 FO This pin is fault output. In case of OLP, SLP, and OCP; this pin is connected to ground. 6 PWM4 PWM dimming signal input pin of channel 4. 7 PWM3 PWM dimming signal input pin of channel 3. 8 PWM2 PWM dimming signal input pin of channel 2. 9 PWM1 PWM dimming signal input pin of channel 1. 11 ADIM This pin is for the reference voltage of the LED current feedback voltage. 12 SLPR This pin is for setting the reference of channel over-voltage protection (short-LED protection). 13 REF This pin is the reference output. Voltage is 5V; current capability is 3mA. 14 VCC This pin is the supply voltage of the controller. 15 FB4 This pin is for current sensing feedback of channel 4. 17 OUT4 This pin is for gate signal to the external balance FET of channel 4. 18 CH4 This pin is for drain voltage of the external balance FET of channel 4. 19 FB3 This pin is for current sensing feedback of channel 3. 20 OUT3 This pin is for gate signal to the external balance FET of channel 3. 21 CH3 This pin is for drain voltage of the external balance FET of channel 3. 22 FB2 This pin is for current sensing feedback of channel 2. 23 OUT2 This pin is for gate signal to the external balance FET of channel 2. 24 CH2 This pin is for drain voltage of the external balance FET of channel 2. 25 FB1 This pin is for current sensing feedback of channel 1. 26 OUT1 This pin is for gate signal to the external balance FET of channel 1. 27 CH1 This pin is for drain voltage of the external balance FET of channel 1. 28 GND This pin is the ground.
© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN7346 • 1.0.0 4 FAN7346 — 4-Channel LED Current Balance Controller Absolute Maximum Ratings Stresses exceeding the absolute maximum ratings may damage the device. The devic e may not function or be operable above the recommended operating conditions and stressi ng the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. Symbol Parameter Min. Max. Unit VIN IC Supply Voltage 10.5 35.0 V TA Operating Temperature Range -40 +125 C TJ Operating Junction Temperature +150 C TSTG Storage Temperature Range -65 +150 C θJA Thermal Resistance Junction-Air (1,2) 70 C/W PD Power Dissipation 1.4 W Notes: 2. Assume no ambient airflow. Pin Breakdown Voltage Pin # Name Value Unit Pin # Name Value Unit
1 OVR 6
V
15 FB4 6
V
2 FB 6 16 VDD 17
3 CMP 6 17 OUT4 17
4 VMIN 6 18 CH4 100
5 FO 6 19 FB3 6
6 PWM4 6 20 OUT3 17
7 PWM3 6 21 CH3 100
8 PWM2 6 22 FB2 6
9 PWM1 6 23 OUT2 17
10 ENA 6 24 CH2 100
11 ADIM 6 25 FB1 6
12 SLPR 6 26 OUT1 17
13 REF 6 27 CH1 100
14 VCC 35 28 GND
© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN7346 • 1.0.0 5 FAN7346 — 4-Channel LED Current Balance Controller
Electrical Characteristics
For typical values; T A = 25°C, VIN = 12V, and -25°C TA 85°C, unless otherwise specifi ed. Specifications to -40°C ~ 125°C are guaranteed by design based on final characterization results. Symbol Parameter Condition Min. Typ. Max. Unit Under-Voltage Lockout Section (UVLO) Vth Start Threshold Voltage 8.5 9.5 10.5 V Vthhys Start Threshold Voltage Hy steresis 0.5 1.0 1.5 V Ist Startup Current V IN=8V 100 300 µA Iop Operating Supply Current V IN=12V, Not Switching 1 3 mA ON/OFF Section Von On-State Input Voltage 1.4 5.0 V Voff Off-Stage Input Voltage 0.7 V RENA Pull-Down Resistor 130 200 270 k Ω Reference Section (Recommend 1µF X7R Capacitor) VREF 5V Regulation Voltage I REF=0mA 4.9 5.0 5.1 V VR-LINE 5V Line Regulation 10 VIN 35V 50 mV VR-LOAD 5V Load Regulation 0 IREF 3mA 50 mV VDD 8.5V Regulation Voltage V IN=12V 8.0 8.5 9.0 V LED Current Section VFBX CH LED Current Reference Voltage VADIM=2V 194 200 206 mV VLREF LED Current Reference Voltage 0.5V VADIM 4V VADIM /10 V VADIM-CLAMPH ADIM Voltage HIGH Clamping Voltage VIN=12V 3.84 4.00 4.16 V VADIM-CLAMPL ADIM Voltage LOW Clamping Voltage VIN=12V 0.45 0.50 0.55 BCH Current Balance Between Channels VADIM=2V -1.5 1.5 % Headroom Voltage Feedback Section VFBR Feedback Reference Voltage 0.95 1.00 1.05 V Ileak Channel Leakage Current PWM ON, VCH=1V 0 100 µA PWM OFF, VCH=30V 0 2 µA AV Open-Loop Gain (3) V VMIN=1V 65 dB Gm Error Amplifier Transconductance V VMIN=1.5V 140 180 220 µmho lsin Output Sink Current V VMIN=0V 70 120 170 µA lsur Output Source Current V VMIN=2V 70 120 170 µA Continued on the following page…
© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN7346 • 1.0.0 6 FAN7346 — 4-Channel LED Current Balance Controller Electrical Characteristics (Continued) For typical values; T A = 25°C, VIN = 12V, and -25°C TA 85°C, unless otherwise specifi ed. Specifications to -40°C ~ 125°C are guaranteed by design based on final characterization results. Symbol Parameter Condition Min. Typ. Max. Unit PWM Dimming Section Vbdim(ON) PWM Dimming On Voltage 2 5 V Vbdim(Off) PWM Dimming Off Voltage 0 0.8 V fbdim PWM Dim Input Frequency Range(3) On Duty Ratio=1% 100 500 Hz tbdimR PWM Dim On Rising Time(3) Ext. Switch Qg=4.3nC 400 ns tbdimF PWM Dim Off Falling Time(3) Ext. Switch Qg=4.3nC 150 ns Soft-Start Section tSS Soft-Start Time(3) VOVR=1V, ILED: 0 to Maximum 10 ms Protection Section VTH,OVR OVR Threshold Voltage 1.35 1.42 1.49 V VTH,OCP OCP Threshold Voltage 0.95 1.00 1.05 V TOCP OCP Shutdown Time(3) 10 µs VTH,SLP SLP Threshold Voltage V SLPR=1V 9.5 10.0 10.5 V TD,SLP SLP Delay(3) 20 µs TD,OLP OLP Delay(3) 20 µs VTH,OLP OLP Threshold Voltage 0.27 0.30 0.33 V TTRIP Internal Thermal Protection Threshold(3) 150 °C TTYH Internal Thermal Protection Hysteresis(3) 25 °C Output Section VGH NMOS Gate High Voltage V IN=12V 8.0 8.5 9.0 V VGL NMOS Gate Low Voltage V IN=12V 0 V VG,UVLO NMOS Gate Voltage with UVLO Activated VIN=7V 0.3 V IG,SOURCE NMOS Gate Drive Source Current V IN=12V 50 150 250 mA IG,SINK NMOS Gate Drive Sink Current V IN=12V 300 500 700 mA Note: 3. These Parameters, although guaranteed, are not 100% tested in production.
© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN7346 • 1.0.0 13 FAN7346 — 4-Channel LED Current Balance Controller 7. Over-Voltage Regulation (OVR) To prevent LED driving vo ltage from exceeding the withstanding voltage of system components, the FAN7346 controls LED driving voltage with OVR pin voltage. The FAN7346 sens es output LED driving voltage through the OVR pin voltage. Resistor divided output voltage is applied to the OVR pin voltage. In FAN7346, OVR voltage us es two kinds of feedback and control: and regulating output voltage during enable off and clamping output voltage during enable on. When ENA pin is LOW, the FAN7346 controls FB voltage to maintain OVR voltage as 1.0V. Through this output voltage control during EN A off, the FAN7346 reaches adequate LED driving voltage before turning ENA on. After ENA pin is HIGH, OVR pin voltage is used for over- voltage regulation. If OVR pin voltage is lower than 1.42V, the FB pin voltage follows headroom control to maintain minimum voltage of drain voltages as 1V. If OVR pin voltage is higher than 1.42V, the FAN7346 controls FB (FB is pulled LOW). Through feedback regulation, OVR pin voltage cannot exceed 1.42V. 8. Over-Current Protection (OCP) Through over-current prot ection, the FAN7346 can protect external balance sw itches from shorted over- current damage. To sense over-current condition, the FAN7346 monitors FBx (FB1~FB4) pin voltage. If FBx voltage is higher than 1V for 20µs, CHx is considered an over-current condition. After sensing OCP condition, CHx dimming switch is turned off. OCP is channel individual and latched protection. If one channel is in OCP condition, other channels keep operating. OCP channel is restarted after UVOL is reset. 9. Error Flag (FO) To make error flag signal, the FAN7346 uses the FO pin. FO pin is open-drain type. During normal operation, the FO pin is open. If using an external pull-up resistor, this signal is HIGH. If used OLP / OCP / SLP protection, the FO pin is connected to ground. If using an external pull-up resistor, this signal is LOW. If a single channel is in protection condition, error-flag signal is detected. Only if all channels are operating normally is the FO pin pulled HIGH.
Figure 32. LCD Backlight Driver
Figure 33. LED Lighting Driver
Figure 34. Multiple Controller Driving
Figure 35. 28-Lead, Small-Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300-Inch, Wide Body specifically the warranty therein, which covers Fairchild products.
© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN7346 • 1.0.0 19 FAN7346 — 4-Channel LED Current Balance Controller