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Technical content
- General description The SSL5021BTS is a highly integrated, high-precision, non-isolated MOSFET/bipolar buck controller. It is intended to drive LED lamps in universal mains non-dimmable lighting applications up to 25 W. The SSL5021BTS is designed for low-ripple applications. The SSL5021BTS operates in Boundary Conduction Mode (BCM) with on-time regulation. Operating in BCM provides a constant output current control with high accuracy. Adaptive switching frequency gives freedom to choose the inductor, which enables the optimization of inductor size, efficiency and EMI. The SSL5021BTS starts up and operates in switching mode directly from an external resistor without dV/dt supply or auxiliary supply. This feature simplifies the V CC supply. It allows a low-cost off-the-shelf inductor to be used, providing flexibility in application design. The SSL5021BTS comes in a compact TSOP6 package. The SSL5031BTS is suitable for high power factor/Low-THD applications with a high-temperature foldback function. The SSL5031CTS is best for high power factor/low-THD applications without a high-temperature foldback function. 2. Features and benefits Driving LED strings from a rectified mains supply, low-ripple (< ±5 %) Small electronic Bill of Materials (BOM) enabling a compact solution and a small, single layer Printed-Circuit Board (PCB) footprint Excellent line and load regulation and LED output current accuracy Efficient BCM operation with: Minimal reverse recovery losses in freewheel diode Zero Current Switching (ZCS) and valley switching for switch turn-on Minimal inductance value and size required High efficiency (up to 91 %) Ultra low IC current during operation (< 150 A) Auto-recovery protections: UnderVoltage LockOut (UVLO) Cycle-by-cycle OverCurrent Protection (OCP) Internal OverTemperature Protection (OTP) Output OverVoltage Protection (OVP) Output Short Protection (OSP) SSL5021BTS Compact low-ripple buck LED driver IC Rev. 2 — 11 March 2015 Product data sheet
Table 1. Quick reference data Table 2. Ordering information
Product data sheet Rev. 2 — 11 March 2015 3 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC 6. Block diagram 7. Pinning information
7.1 Pinning
Fig 1. Block diagram DDD 9&& ,616 *1' '(0293 &203 217,0( 5(*8/$725 9$//(< '(7(&7,21 /2*,& &21752/ $1' 3527(&7,21 6833/< %$1'*$3 5(*8/$725 325 $1$/2* &219(57(5 7(03)2/' '(0$* 2&3 293 %/$1. Fig 2. SSL5021BTS pin configuration (TSOP6) ,616 66/%76 &203 9&& *1' 6: '(0293 DDD
7.2 Pin description
8.1 Converter operation
shows the basic application diagram for bipolar. Mode (DCM). Figure 5 shows the waveforms. When the internal switch switches off at t1, IL drops proportionally to the value of VOUT. IL reaches zero, after a short delay (t3 to t00), a new switching cycle starts. Table 3. Pin description
Product data sheet Rev. 2 — 11 March 2015 5 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC
8.2 On-time control
When measuring the inductor current IL using sense resistor R4, the on-time is regulated so that the average regulated voltage on pin ISNS (Vintregd(AV)ISNS) equals an internal reference voltage. IL can be calculated with Equation 1: (1) Where:
- 0.09 = ISNS bond wire resistance.
- is the buck topology duty cycle.
8.3 Valley detection
After IL has decreased to zero at t3, the LEDP voltage starts to oscillate around the bus voltage (VIN) minus output voltage level (VOUT), with amplitude output voltage (VOUT) and frequency (fring). Valley detection is a special circuit that is integrated in the SSL5021BTS. It senses when the LEDP voltage reaches its lowest level (valley) through DEMOVP pin connection. If a valley is detected, the internal switch is switched on again. As a result, the switch-on switching losses are reduced. Fig 4. SSL5021BTS basic application diagram for bipolar DDD & /('V /('39&& ,616 *1' &203 '(0293 IL Vintregd AV ISNS
Product data sheet Rev. 2 — 11 March 2015 6 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC
8.4 Start-up current
The supply current for the IC is supplied by resistor R3. The IC drawns an additional start-up current (ICC(startup)) just before VCC reaches the start-up voltage level (Vstartup). So the supply current in operating mode is lower than during start-up conditions, preventing lamp flicker when the mains voltage is increased or decreased slowly. Figure 6 shows the basic behavior. Fig 5. Buck waveforms and valley detection DDD 9287 9,1 W WW W W PDJQHWL]DWLRQ GHPDJQHWL]DWLRQ LQWHUQDO VZLWFK JDWH 9*$7( 9/('3 9DOOH\\ WLPH
Product data sheet Rev. 2 — 11 March 2015 7 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC
8.5 Leading-Edge Blanking (LEB)
To prevent false detection of overcurrent, a blanking time following switch-on is implemented. When the internal switch turns on, a short current spike can occur because of the discharge capacitance of the MOSFET/bipolar (Q1) drain/collector node.
8.6 Protections
The IC incorporates the following protections:
- UnderVoltage LockOut (UVLO)
- Cycle-by-cycle OverCurrent Protection (OCP)
- Internal OverTemperature Protection (OTP)
- Cycle-by-cycle maximum on-time protection
- Output OverVoltage Protection
- Output Short Protection (OSP)
8.6.1 UnderVoltage LockOut (UVLO)
When voltage on VCC pin drops to below Vth(UVLO), the IC stops switching. An attempt is made to restart IC when the voltage on the VCC pin > Vstartup.
8.6.2 Cycle-by-cycle OverCurrent Protection (OCP)
The SSL5021BTS incorporates a built-in peak current detector. It triggers when the voltage at the ISNS pin reaches the peak level VI(max)ISNS. A resistor connected to ISNS pin senses the current through inductor IL. The maximum current in inductor, IL(max) equals: (2) Fig 6. Start-up current waveform DDD 9&& 9*$7( ,&& ,&& VWDUWXS ,&& RSHU 99&& 9VWDUWXS ILm a x VI max ISNS
Product data sheet Rev. 2 — 11 March 2015 8 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC The sense circuit is activated after the leading-edge blanking time (tleb). Because the LED current is half the peak current by design, the sense circuit automatically provides protection for the maximum LED current during operation. A propagation delay exists between the overcurrent detection and the actual switch switch-off. Due to this delay, the actual peak current is slightly higher than the OCP level set by the resistor connected in series with the ISNS pin.
8.6.3 OverTemperature Protection (OTP)
The converter stops switching when the internal OTP function is triggered at the IC junction temperature Tpl(IC). The safe-restart protection is triggered and the IC resumes switching when the IC temperature drops to below Trst(IC).
8.6.4 Cycle-by-cycle maximum on-time protection
Measuring the inductor current IL using sense resistor R4 regulates the on-time. The on-time is limited to a fixed value (ton(max)). It protects the system and the IC when the ISNS pin is shorted or when the system works at very low mains voltage.
8.6.5 Output OverVoltage Protection (OVP)
An accurate output OVP is implemented by measuring the voltage at the DEMOVP pin during the secondary stroke. The resistive divider connected between the LEDP node and the DEMOVP pin sets the maximum LED voltage. An internal counter prevents false OVP detection because of noise on the DEMOVP pin. After three continuous cycles with a DEMOVP pin voltage above the OVP level, the OVP protection is triggered. The over voltage protection triggers a restart sequence: A discharge current (I CC(dch)) is enabled and discharges the voltage on the VCC pin to below Vrst(latch). When Vrst(latch) is reached, the system restarts.
8.6.6 Output Short Protection (OSP)
The converter operates in Discontinuous Conduction Mode (DCM). A new cycle is only started after the previous cycle has ended. The end of the cycle is detected by measuring the voltage on the DEMOVP pin. When the DEMOVP pin voltage drops to below the demagnetization level (Vth(comp)DEMOVP) and a valley is detected, a new cycle starts. When output is shorted, the demagnetization is not finalized within the 40 s. The converter still regulates the adjusted output current and the on-time is reduced to a safe value by this feedback. The reduced on-time in combination with very long demagnetization time prevents that the converter is damaged or excessive dissipation occurs. A blanking time (t sup(xfmr_ring)) is implemented at the start of the secondary stroke to prevent false demagnetization detection.
Product data sheet Rev. 2 — 11 March 2015 9 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC
8.7 Supply management
The IC starts up when the voltage on the VCC pin increases to exceed Vstartup. The IC locks out (stops switching) when the voltage on the VCC pin drops to below Vth(UVLO). The hysteresis between the start and stop levels allows the VCC capacitor to supply the IC during zero-crossings of the mains. The SSL5021BTS incorporates an internal clamping circuit to limit the voltage on the VCC pin. The clamp limits the voltage on the VCC pin to the maximum value, Vclamp(VCC). If the maximum current of the external resistor minus the current consumption of the IC is lower than the limiting value of IVCC in Table 4, no external Zener diode is required.
8.8 PTC or NTC function a nd high-temperature foldback
The PTC function or NTC function can be used as a control method for LED thermal protection. The PTC resistor which is connected to DEMOVP pin senses the temperature. When the voltage on DEMOVP pin is higher than the foldback level (Vth(fold)), the on-time is reduced with the increased DEMOVP pin voltage. Then the average LED current is reduced. When the temperature keeps increasing, the V th(ovp) is exceeded. The converter stops switching. The IC restarts when OVP is triggered. This feature is optional as shown in Figure 7 and Figure 8. PTC is normally shorted.
[1] The current into the VCC pin must not exceed the maximum I (VCC) value. [2] An internal clamp sets the supply voltage and current limits. [3] Equivalent to discharge a 100 pF capacitor through a 1.5 k series resistor. pin down to 0 V over a 1 resistor. Table 4. Limiting values In accordance with the Absolute Maximum Rating System (IEC 60134). Table 5. Thermal characteristics
259 K/W
152 K/W
Table 6. Characteristics the IC; unless otherwise specified.
[1] The start-up voltage and the clamp voltage are correlated. [3] The minimum on-time is only effective when OCP is triggered. Table 6. Characteristics …continued the IC; unless otherwise specified.
Product data sheet Rev. 2 — 11 March 2015 13 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC 12. Application information (1) R3b, R6b, C1 and C2 are the parts for the 230 V (AC) mains application. Short R3b and R6b out and reduce C1 and C2 voltage rating for the 120 V (AC) mains application. (2) RT1 is optional. It is normally shorted. Fig 7. SSL5021BTS application diagram for MOSFET 9PDLQV 9PDLQV 5D5 /('V /('3 '(0293 *1' &203 9&& ,616 DDD
Product data sheet Rev. 2 — 11 March 2015 14 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC (1) R3b, R6b, C1 and C2 are the parts for the 230 V (AC) mains application. Short R3b and R6b out and reduce C1 and C2 voltage rating for the 120 V (AC) mains application. (2) RT1 is optional. It is normally shorted. Fig 8. SSL5021BTS application diagram for bipolar 9PDLQV 9PDLQV 5D5 /('V /('3 '(0293 *1' &203 9&& ,616 DDD
Product data sheet Rev. 2 — 11 March 2015 15 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC 13. Package outline Fig 9. Package outline SOT457 (TSOP6) 5()(5(1&(6287/,1( 9(56,21 (8523($1 ,(& -('(& -(,7$ 627 6& Z%0ES H SLQ LQGH[ $ GHWDLO; Y 0 $ VFDOH F PP 3ODVWLFVXUIDFHPRXQWHGSDFNDJH 7623 OHDGV 627 PP H ',0(16,216 PPDUHWKHRULJLQDOGLPHQVLRQV
Table 7. Abbreviations
Table 8. Revision history Modifications: • The data sheet status has changed from Preliminary to Product.
- Text and graphics have been updated throughout the data sheet. SSL5021BTS v.1 20141015 Preliminary data sheet - -
Product data sheet Rev. 2 — 11 March 2015 18 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC 16. Legal information
16.1 Data sheet status
[1] Please consult the most recently issued document before initiating or completing a design. [2] The term ‘short data sheet’ is explained in section “Definitions”. [3] The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status information is available on the Internet at URL http://www.nxp.com.
16.2 Definitions
Draft — The document is a draft version only. The content is still under internal review and subject to formal approval, which may result in modifications or additions. NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information. Short data sheet — A short data sheet is an extract from a full data sheet with the same product type number(s) and title. A short data sheet is intended for quick reference only and should not be relied upon to contain detailed and full information. For detailed and full information see the relevant full data sheet, which is available on request via the local NXP Semiconductors sales office. In case of any inconsistency or conflict with the short data sheet, the full data sheet shall prevail. Product specification — The information and data provided in a Product data sheet shall define the specification of the product as agreed between NXP Semiconductors and its customer, unless NXP Semiconductors and customer have explicitly agreed otherwise in writing. In no event however, shall an agreement be valid in which the NXP Semiconductors product is deemed to offer functions and qualities beyond those described in the Product data sheet.
16.3 Disclaimers
Limited warranty and liability — Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. NXP Semiconductors takes no responsibility for the content in this document if provided by an information source outside of NXP Semiconductors. In no event shall NXP Semiconductors be liable for any indirect, incidental, punitive, special or consequential damages (including - without limitation - lost profits, lost savings, business interruption, costs related to the removal or replacement of any products or rework charges) whether or not such damages are based on tort (including negligence), warranty, breach of contract or any other legal theory. Notwithstanding any damages that customer might incur for any reason whatsoever, NXP Semiconductors’ aggregate and cumulative liability towards customer for the products described herein shall be limited in accordance with the Terms and conditions of commercial sale of NXP Semiconductors. Right to make changes — NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. This document supersedes and replaces all information supplied prior to the publication hereof. Suitability for use — NXP Semiconductors products are not designed, authorized or warranted to be suitable for use in life support, life-critical or safety-critical systems or equipment, nor in applications where failure or malfunction of an NXP Semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental damage. NXP Semiconductors and its suppliers accept no liability for inclusion and/or use of NXP Semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer’s own risk. Applications — Applications that are described herein for any of these products are for illustrative purposes only. NXP Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Customers are responsible for the design and operation of their applications and products using NXP Semiconductors products, and NXP Semiconductors accepts no liability for any assistance with applications or customer product design. It is customer’s sole responsibility to determine whether the NXP Semiconductors product is suitable and fit for the customer’s applications and products planned, as well as for the planned application and use of customer’s third party customer(s). Customers should provide appropriate design and operating safeguards to minimize the risks associated with their applications and products. NXP Semiconductors does not accept any liability related to any default, damage, costs or problem which is based on any weakness or default in the customer’s applications or products, or the application or use by customer’s third party customer(s). Customer is responsible for doing all necessary testing for the customer’s applications and products using NXP Semiconductors products in order to avoid a default of the applications and the products or of the application or use by customer’s third party customer(s). NXP does not accept any liability in this respect. Limiting values — Stress above one or more limiting values (as defined in the Absolute Maximum Ratings System of IEC 60134) will cause permanent damage to the device. Limiting values are stress ratings only and (proper) operation of the device at these or any other conditions above those given in the Recommended operating conditions section (if present) or the Characteristics sections of this document is not warranted. Constant or repeated exposure to limiting values will permanently and irreversibly affect the quality and reliability of the device. Terms and conditions of commercial sale — NXP Semiconductors products are sold subject to the general terms and conditions of commercial sale, as published at http://www.nxp.com/profile/terms , unless otherwise agreed in a valid written individual agreement. In case an individual agreement is concluded only the terms and conditions of the respective agreement shall apply. NXP Semiconductors hereby expressly objects to applying the customer’s general terms and conditions with regard to the purchase of NXP Semiconductors products by customer. No offer to sell or license — Nothing in this document may be interpreted or construed as an offer to sell products that is open for acceptance or the grant, conveyance or implication of any license under any copyrights, patents or other industrial or intellectual property rights. Document status[1][2] Product status[3] Definition Objective [short] data sheet Development This document contains data from the objective specification for product development. Preliminary [short] data sheet Qualification This document contains data from the preliminary specification. Product [short] data sheet Production This document contains the product specification.
Product data sheet Rev. 2 — 11 March 2015 19 of 20 NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC Export control — This document as well as the item(s) described herein may be subject to export control regulations. Export might require a prior authorization from competent authorities. Quick reference data — The Quick reference data is an extract of the product data given in the Limiting values and Characteristics sections of this document, and as such is not complete, exhaustive or legally binding. Non-automotive qualified products — Unless this data sheet expressly states that this specific NXP Semiconductors product is automotive qualified, the product is not suitable for automotive use. It is neither qualified nor tested in accordance with automotive testing or application requirements. NXP Semiconductors accepts no liability for inclusion and/or use of non-automotive qualified products in automotive equipment or applications. In the event that customer uses the product for design-in and use in automotive applications to automotive specifications and standards, customer (a) shall use the product without NXP Semiconductors’ warranty of the product for such automotive applications, use and specifications, and (b) whenever customer uses the product for automotive applications beyond NXP Semiconductors’ specifications such use shall be solely at customer’s own risk, and (c) customer fully indemnifies NXP Semiconductors for any liability, damages or failed product claims resulting from customer design and use of the product for automotive applications beyond NXP Semiconductors’ standard warranty and NXP Semiconductors’ product specifications. Translations — A non-English (translated) version of a document is for reference only. The English version shall prevail in case of any discrepancy between the translated and English versions.
16.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. GreenChip — is a trademark of NXP Semiconductors N.V. 17. Contact information For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com
NXP Semiconductors SSL5021BTS Compact low-ripple buck LED driver IC © NXP Semiconductors N.V. 2015. All rights reserved. For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com Date of release: 11 March 2015 Document identifier: SSL5021BTS Please be aware that important notices concerning this document and the product(s) described herein, have been included in section ‘Legal information’. 18. Contents 8.6.2 Cycle-by-cycle OverCurr ent Protection (OCP) . 7 8.6.4 Cycle-by-cycle maximum on-time protection . . 8