CS1680-FZZ

CS1680 Dimmable LED Driver IC for Low-voltage Lighting Features Overview • Best-in-class Transformer Compatibility The CS1680 is a cascade boost-buck dimmable LED driver for the 12V halogen lamp-replacement market. The CS1680 uses a Cirrus Logic proprietary intelligent digital control that provides exceptional single-lamp and multi-lamp transformer compatibility for non-dimmer systems and dimmer systems paired with electronic and magnetic low-voltage transformers. - Magnetic Transformers - Electronic Transformers • Best-in-class Dimmer Compatibility - Leading-edge (TRIAC) Dimmers - Trailing-edge Dimmers • High Efficiency - Up to 80% for CS1680-00 Applications - Up to 83% for CS1680-02 Applications • Flicker-free Dimming • 5% Minimum Dimming Level • Cascade Boost-buck Topology with Constant-current Output - CS1680-00 Output Voltage 15V - CS1680-02 Output Voltage 21V • • • • • Fast Startup Tight LED Current Regulation: Better than ±10% >0.9 Power Factor on Magnetic Transformers Soft Start Protections: The CS1680 integrates a continuous conduction mode (CCM) boost converter that provides transformer compatibility and dimmer compatibility. An adaptive digital algorithm controls the boost stage and dimmer compatibility operation mode to enable flicker-free operation down to 5% output current with leading-edge and trailing-edge dimmers. Applications • MR16 Lamps • All 12VAC/VDC Low-voltage Lighting Applications - Output Open/Short - Boost Overvoltage - Overcurrent Detection - External Overtemperature Using NTC Ordering Information See page 15. LB S T Vrect VBST Rrect R2 D1 D3 RB S T VAC D6 Q1 QB S T R4 C2 CS1680 BUCKZCD U1 7 D2 D4 Z1 C1 C3 Z2 C4 11 LED - QCLA MP 9 C5 BUCKGD GPIO eOTP BSTSENSE QB UCK 12 13 2 RS RB S T(S ense) CTRL1 16 RCTRL1 Cirrus Logic, Inc. http://www.cirrus.com COUT LB UCK VDD BUCKSENSE 3 R3 DB UCK BSTGD R5 6 CB S T BSTOUT CLAMP Q2 Crect 12VAC/VDC 5 RCLA MP 15 14 D5 R1 LED + DB S T Copyright  Cirrus Logic, Inc. 2014 (All Rights Reserved) GND 4 CNTC CTRL2 1 RCTRL2 RB UCK(S ense) NTC OCT’14 DS1055F1 CS1680 1. INTRODUCTION BSTOUT 15 Iref 20k VAC MUX ADC Voltage Regulator 6 POR 14 + - VDD VZ VST(th) VSTP(th) 20k VDD BSTGD 5 Buck Blank 2 3 ZCD VBSTOCP(th) + - 3 VBSTPK(th) Buck Peak Ctrl DAC - BUCKZCD 13 BUCKSENSE 16 CTRL1 CTRL2 VBUCKPK(th) VDD 7 VDD ICONNECT - CLAMP 9 VBUCKOCP(th) + DAC GPIO GND + Boost Peak Ctrl + 4 VBUCKZCD(th) OCP BSTSENSE BUCKGD BST Blank BOCP + 12 + 11 MUX 1 VCONNECT (th) 2 eOTP Figure 1. CS1680 Block Diagram A typical schematic using the CS1680 for boost-buck applications is shown on the previous page. A startup circuit provides a low-impedance path to improve electronic transformer compatibility. The GPIO pin is used to disable the startup circuit when normal operation is reached. The CS1680 power supply is connected to an external power supply network. A linear regulator at the output of the boost converter provides steady-state operating current to the IC. The rectified input voltage is sensed as a current into pin VAC and is used to control the adaptive transformer and dimmer compatibility algorithm and extract the phase of the input voltage for output dimming control. During steady-state operation, the boost stage operates in continuous conduction mode (CCM) to boost the input voltage. This operation allows the boost stage to 2 provide transformer and dimmer compatibility, reduces bulk capacitor ripple current, and provides a regulated input voltage to the buck stage. The output voltage of the CCM boost is sensed by the current into the boost output voltage sense pin (BSTOUT). The buck stage is implemented with peak-current mode control. Voltage across an external user-selected resistor is sensed through pin BUCKSENSE to control the peak current through the buck stage inductor. Leading-edge blanking on pin BUCKSENSE prevents false triggering. When an external negative temperature coefficient (NTC) thermistor is connected to the eOTP pin, the CS1680 monitors the system temperature, allowing the controller to reduce the output current of the system. If the temperature reaches a designated high set point, the IC is shutdown and stops switching. DS1055F1 CS1680 2. PIN DESCRIPTION Peak Current CTRL2 1 16 CTRL1 Boost Stage Constant External Overtemperature Protection eOTP 2 15 BSTOUT Boost Output Voltage Sense Boost Stage Current Sense BSTSENSE 3 14 VAC Rectifier Voltage Sense Ground GND 4 13 BUCKSENSE Buck Stage Current Sense Boost Gate Driver BSTGD 5 12 BUCKGD Buck Gate Driver IC Supply Voltage VDD 6 11 CLAMP Voltage Clamp Current Source General Purpose Input/Output GPIO 7 10 NC No Connect No Connect NC 8 9 BUCKZCD Buck Stage Zero-current Detect 16-lead TSSOP Figure 2. CS1680 Pin Assignments Pin Name Pin # I/O CTRL2 1 IN Peak Current — Connect a resistor to this pin to set the comparator threshold to reflect the desired boost peak current in Trailing Edge Electronic Transformer Mode (Mode 2). eOTP 2 IN External Overtemperature Protection — Connect an external NTC thermistor to this pin, allowing the internal A/D converter to sample the change to NTC resistance. BSTSENSE 3 IN Boost Stage Current Sense — The current flowing in the boost stage FET is sensed across a resistor. The resulting voltage is applied to this pin and digitized for use by the boost stage computational logic to determine the FET duty cycle. GND 4 PWR Ground — Common reference. Current return for both the input signal portion of the IC and the gate driver. BSTGD 5 OUT Boost Gate Driver — Gate drive for the boost stage power FET. VDD 6 PWR IC Supply Voltage — Connect a storage capacitor to this pin to serve as a reservoir for operating current for the device, including the gate drive current to the power transistor. GPIO 7 IN/OUT General Purpose Input/Output — Used to drive the FET gate for the startup circuit. NC 8 IN No Connect — Leave pin not connected. BUCKZCD 9 IN Buck Stage Zero-current Detect — Buck stage inductor sensing input. The pin is connected to the drain of the buck stage power FET with a capacitor. NC 10 IN No Connect — Leave pin not connected. CLAMP 11 OUT Voltage Clamp Current Source — Connect to a voltage clamp circuit on the output of the boost stage. BUCKGD 12 OUT Buck Gate Driver — Gate drive for the buck stage power FET. BUCKSENSE 13 IN Buck Stage Current Sense — The current flowing in the buck stage FET is sensed across a resistor. The resulting voltage is applied to this pin and digitized for use by the buck stage computational logic to determine the FET duty cycle. VAC 14 IN Rectifier Voltage Sense — A current proportional to the rectified line voltage is fed into this pin. The current is measured with an A/D converter. BSTOUT 15 IN Boost Output Voltage Sense — A current proportional to the boost output is fed into this pin. The current is measured with an A/D converter. CTRL1 16 IN Boost Stage Constant — Connect a resistor to this pin to set the constant ratio for the boost stage current calculations in Leading Edge Electronic Transformer Mode (Mode 3). DS1055F1 Description 3 CS1680 3. CHARACTERISTICS AND SPECIFICATIONS 3.1 Electrical Characteristics Typical characteristics conditions: - TA = 25 °C, VDD = 12V, GND = 0 V - All voltages are measured with respect to GND. - Unless otherwise specified, all currents are positive when flowing into the IC. Parameter Minimum/Maximum characteristics conditions: - TJ = -40°C to +125 °C, VDD = 11V to 17V, GND = 0 V Condition Symbol Min Typ Max Unit After Turn-on VDD 11 - 17 V Turn-on Threshold Voltage VDD Increasing VST(th) - 8.5 - V Turn-off Threshold Voltage (UVLO) VDD Decreasing VSTP(th) - 7.5 - V VDD Supply Voltage Operating Range GPIO Low (Note 1) VDD > VST(th) KGPIO(low) - 50.0 - % Zener Voltage (Note 2) IDD = 20mA VZ 18.5 - 19.8 V VDD