UM1660 Low Power DC/DC Boost Converter UM1660S SOT23-5 UM1660DA DFN6 2.0×2.0 General Description The UM1660 is a PFM controlled step-up DC-DC converter with a switching frequency up to 1MHz. The device is ideal to generate output voltage for small to medium LCD bias supplies and white LED backlight supplies from a single cell Li-Ion battery. The part can also be used to generate standard 3.3V/5V to 12V power conversions. With a high switching frequency of 1MHz, a low profile and small board area solution can be achieved using a chip coil and an ultra small ceramic output capacitor. The UM1660 has an internal 400mA switch current limit, offering lower output voltage ripple. The low quiescent current (typically 36µA) together with an optimized control scheme, allows device operation at very high efficiencies over the entire load current range. Applications Features Pin Configurations Top View 5 (Top View) SW 1 GND 2 FB 3 2.0V to 6.0V Input Voltage Range Adjustable Output Voltage up to 28V 400mA Internal Switch Current Up to 1MHz Switching Frequency 36µA Typical No Load Quiescent Current 1µA Maximum Shutdown Current Internal Soft-Start Available in Tiny SOT23-5 and DFN6 2.0×2.0 Packages 5 4 PHO VIN 1 4 EN 2 M LCD Bias Supply White LED Supply for LCD Backlights Digital Still Camera PDAs, Organizers and Handheld PCs Cellular Phones Standard 3.3V/5V to 12V Conversion 3 M: Month Code UM1660S SOT23-5 VIN 1 6 SW GND 2 5 NC EN 3 4 FB AAG M (Top View) Marking Pin1 M: Month Code UM1660DA DFN6 2.0×2.0 ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 1/15 UM1660 Ordering Information Part Number Packaging Type Marking Code UM1660S SOT23-5 PHO UM1660DA DFN6 2.0×2.0 AAG Shipping Qty 3000pcs/7Inch Tape & Reel 3000pcs/7Inch Tape & Reel Pin Description Pin Number UM1660S UM1660DA Symbol Function 1 6 SW 2 2 GND 3 4 FB 4 3 EN 5 1 VIN Connect the inductor and the Schottky diode to this pin. This is the switch pin and is connected to the drain of the internal power MOSFET. Ground This is the feedback pin of the device. Connect this pin to the external voltage divider to program the desired output voltage. This is the enable pin of the device. Pulling this pin to ground forces the device into shutdown mode reducing the supply current to less than 1µA. This pin should not be left floating and needs to be terminated. Supply voltage pin - 5 NC Not connected Absolute Maximum Ratings Over operating free-air temperature (unless otherwise noted) (Note 1) Symbol Parameter Value VIN VFB, VEN VSW Supply Voltage on VIN (Note 2) Voltages on FB, EN (Note 2) Switch Voltage on SW (Note 2) PD Continuous Power Dissipation SOT23-5 at TA = 25°C DFN6 2.0×2.0 TJ Operating Junction Temperature Unit -0.3 to +7.0 V -0.3 to VIN +0.3 V 30 V 0.35 0.7 -40 to +150 W °C TSTG Storage Temperature Range -65 to +150 °C Maximum Lead Temperature for Soldering 10 TL +260 °C seconds Note 1: 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 conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. Note 2: All voltage values are with respect to network ground terminal. ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 2/15 UM1660 Recommended Operating Conditions Symbol Parameter Min VIN Input Voltage Range VOUT Output Voltage Range L Inductor (Note 3) f Switching Frequency (Note 3) CIN Input Capacitor (Note 3) COUT Output Capacitor (Note 3) TA Operating Ambient Temperature TJ Operating Junction Temperature Note 3: Refer to application section for further information. Typ 2.0 2.2 Max Unit 6.0 28 V V μH MHz μF μF °C °C 10 1 4.7 1 -40 -40 85 125 Function Block Diagram SW Under Voltage Lockout Bias Supply VIN 400ns Min Off Time Error Comparator - FB S + RS Latch Logic VREF=1.233V Power MOSFET N-Channel Gate Driver R Current Limit + EN - 6μs Max On Time RSENSE Soft Start GND Figure 1. UM1660 function block diagram ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 3/15 UM1660 Electrical Characteristics (VIN= 2.4 V, EN = VIN, CIN=4.7μF, COUT=1μF, L=10μH, TA = -40°C to 85°C, typical values are at TA = 25°C, unless otherwise noted) Symbol Parameter Test Conditions Min Typ Max Unit SUPPLY CURRENT VIN Input Voltage Range 2.0 6.0 V IOUT=0mA, Operating Quiescent IQ not switching 36 70 μA Current VFB = 1.3V ISD Shutdown Current EN=GND 0.1 1 μA Under-voltage VUVLO 1.5 1.8 V Lockout Threshold ENABLE EN High Level Input VIH 1.3 V Voltage EN Low Level Input VIL 0.4 V Voltage EN Input Leakage IL EN=GND or VIN 0.1 1 μA Current POWER SWITCH AND CURRENT LIMIT Maximum Switch VSW 28 V Voltage tON Maximum On Time 4 6 7.5 μs tOFF Minimum Off Time 250 400 550 ns MOSFET On RDS(ON) VIN = 2.4V, ISW=50mA 750 1200 mΩ Resistance MOSFET Leakage VSW =28V 1 10 μA Current MOSFET Current ILIM 350 400 450 mA Limit OUTPUT Adjustable Output VOUT VIN 28 V Voltage Range Internal Voltage VREF 1.233 V Reference Feedback Input Bias IFB VFB = 1.3V 1 μA Current Feedback Trip Point VFB 2.0V ≤ VIN ≤ 6.0V 1.196 1.233 1.270 V Voltage 2.0V ≤ VIN ≤ 6.0V ; Line Regulation VOUT =18V; 0.05 %/V (Note 4) ILOAD=10mA VIN = 2.4V; Load Regulation %/ VOUT =18V; 0.15 (Note 4) mA 0mA﹤IOUT﹤25mA; Note 4: The line and load regulation depend on the external component selection. ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 4/15 UM1660 Operation The UM1660 features a constant off-time control scheme. Operation can be best understood by referring to the function block diagram. The converter monitors the output voltage, and as soon as the feedback voltage falls below the reference voltage of typically 1.233V, the internal switch turns on and the current ramps up. The switch turns off as soon as the inductor current reaches the internally set peak current of typically 400mA. The second criteria that turns off the switch is the maximum on-time of 6µs (typical). This is just to limit the maximum on-time of the converter to cover for extreme conditions. As the switch is turned off the external Schottky diode is forward biased delivering the current to the output. The switch remains off for a minimum of 400ns (typical), or until the feedback voltage drops below the reference voltage again. Using this PFM peak current control scheme the converter operates in discontinuous conduction mode (DCM) where the switching frequency depends on the output current, which results in very high efficiency over the entire load current range. Peak Current Control The internal switch turns on until the inductor current reaches the typical dc current limit (I LIM) of 400mA. There is approximately a 100ns delay from the time the current limit is reached and when the internal logic actually turns off the switch. During this 100ns delay, the peak inductor current will increase. This increase demands a larger saturation current rating for the inductor. This saturation current can be approximated by the following equation: I peak(typ ) I LIM Vin 100 ns L The higher the input voltage and the lower the inductor value, the greater the peak current. Soft-Start All inductive step-up converters exhibit high inrush current during start-up if no special precaution is made. This can cause voltage drops at the input rail during start up and may result in an unwanted or early system shut down. The UM1660 limits this inrush current by increasing the current limit in two steps from ILIM/4 for 256 cycles to ILIM/2 for the next 256 cycles, and then full current limit. Enable Pulling the enable pin (EN) to ground shuts down the device reducing the shutdown current to 1µA (typical). Since there is a conductive path from the input to the output through the inductor and Schottky diode, the output voltage is equal to the input voltage during shutdown. The enable pin needs to be terminated and should not be left floating. Using a small external transistor disconnects the input from the output during shutdown as shown in the figure below. ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 5/15 UM1660 R3 47k L1 10µH V IN = 2.0 - 6 V SW VIN C1 4.7µF EN R1 2.2M C2 1µF UM1660 GPIO VOUT 18V/10mA D1 C FF 22pF FB GND C2 0.1µF (Optional) R2 160k Figure 2. Disconnect the input from the output during shutdown using external transistor Under-voltage Lockout An under-voltage lockout prevents misoperation of the device at input voltages below typical 1.5V. When the input voltage is below the under-voltage threshold the main switch is turned off. Typical Application Circuit L1 10µH V IN = 2.0 - 6V VOUT SW VIN C IN 4.7µF D1 R1 UM1660 CFF COUT 1µF FB EN GND R2 Figure 3. Standard DC/DC Boost Supply The output voltage is calculated as: Vout 1.233 (1 R1 ) R2 We can use a PWM signal on the enable pin of UM1660 to adjust the white LED brightness (see figure 4 below). When adding the PWM signal to EN pin, the UM1660 is turned on or off by the PWM signal, so the LEDs operate at either zero or full current. The average LED current increases proportionally with the duty cycle of the PWM signal. The magnitude of the PWM signal should be higher than the minimum enable voltage of EN pin (1.3V) and lower than the Vin, in order to let the dimming control perform correctly. The frequency range of the PWM signal is from 50Hz to 10 kHz. ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 6/15 UM1660 L1 10µH VIN =2.7- 6V C IN 4.7 µF D1 SW VIN D2 30V (Optional) COUT 1µF UM1660 PWM EN FB 50 Hz to 10kHz Rs 82Ω GND Figure 4. White LED Supply with Adjustable Brightness Control Using a PWM Signal on the Enable Pin We also can adjust the white LED brightness using an analog signal on the feedback pin (see figure 5 below). Add a DC voltage to the FB pin, and adjust the LED current by change the DC voltage, which control the brightness. The LED current is calculated as: I RS VFB R1 R2 V ADJ R1 RS R2 L1 10µH VIN =2.7- 6V D1 VIN C IN 4.7 µF SW UM1660 FB EN D2 30V (Optional) Cout * 100nF VFB R1 GND Rs V ADJ R2 * A smaller output capacitor value for Cout causes a larger LED ripple Figure 5. White LED Supply with Adjustable Brightness Control Using an Analog Signal on the Feedback Pin ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 7/15 UM1660 Typical Operating Characteristics （CIN=4.7μF, COUT=1μF, L=10μH, TA=25℃, unless otherwise noted） Efficiency vs Output Current 100% 100% 90% 90% 80% 80% 70% 70% Efficiency (%) Efficiency (%) Efficiency vs Output Current 60% 50% 40% 60% 50% 40% VIN=5.0V 30% 20% 30% VIN=3.7V VIN=2.4V VO=18V, L=10μH 10% L=10uH VIN=3.7V, VO=18V 20% L=3.3uH 10% 0.1 1 10 100 0.1 1 Output Current (mA) 10 100 Output Current (mA) Efficiency vs Input Voltage Quiescent Current vs Input Voltage 50 90% 45 Quiescent Current (uA) Efficiency (%) 85% 80% 75% 70% Io=10mA VO=18V, L=10μH 65% Io=5mA 40 35 30 25 20 15 TA=-30℃ 10 TA=25℃ 5 TA=85℃ 0 60% 1 2 3 4 5 1 6 2 Input Voltage (V) 3 4 5 6 Input Voltage (V) Feedback Voltage vs Temperature Switch Current Limit vs Temperature 430 1.28 410 1.27 390 Switch Current Limit (mA) Feedback Voltage (V) 1.26 1.25 1.24 1.23 VIN=2.4V 1.22 VIN=3.6V 370 350 330 310 290 270 VIN=5.0V VIN=5.0V 1.21 250 1.2 -40 -20 0 20 40 Temperature (℃) 60 80 100 230 -40 -20 0 20 40 60 80 100 Tem perature (℃) ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 8/15 UM1660 Typical Operating Characteristics (Continued) （CIN=4.7μF, COUT=1μF, L=10μH, TA=25℃, unless otherwise noted） Output Temperature Output Voltage Voltage vsvs Temperature RDS(ON) vs Temperature Static Drain-Source on-state Resistance (mΩ) 19.00 18.80 Output Voltage (V) 18.60 18.40 18.20 18.00 17.80 17.60 VIN=5.0V, IO=10mA 17.40 17.20 17.00 -40 -20 0 20 40 60 80 100 Temperature(℃) 1100 1000 900 800 700 600 500 VIN=3.6V, 400 300 -40 -20 0 20 40 60 80 100 Temperature (℃) Static Drain-Source on-state Resistance (mΩ) RDS(ON) vs Input Voltage Line Transient Response 1100 VIN=2.4V to 3.4V 1000 900 800 700 VO 100mV/div 600 500 400 200μs/div VO=18V, IO=10mA 300 1 2 3 4 5 6 Input Voltage (V) Load Transient Response IO=1mA to 10mA Start-up Behavior VOUT 5V/div VO 100mV/div 200μs/div VIN=3.3V, VO=18V EN 2V/div 200μs/div VIN=3.6V, VO=18V, IO=10mA ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 9/15 UM1660 Applications Information Inductor Selection, Maximum Load Current Since the PFM peak current control scheme is inherently stable, the inductor value does not affect the stability of the regulator. The selection of the inductor together with the nominal load current, input and output voltage of the application determines the switching frequency of the converter. Depending on the application, inductor values between 2.2µH up to 33µH are recommended. The maximum inductor value is determined by the maximum on time of the switch, typically 6µs. The peak current limit of 400mA (typically) should be reached within this 6µs period for proper operation. The inductor value determines the maximum switching frequency of the converter. Therefore, select the inductor value that ensures the maximum switching frequency at the converter maximum load current is not exceeded. The maximum switching frequency is calculated by the following formula: fs max Vinmin (Vout Vin) Ip L Vout Where: IP = Peak current as described in the previous peak current control section L = Selected inductor value Vinmin = The highest switching frequency occurs at the minimum input voltage If the selected inductor value does not exceed the maximum switching frequency of the converter, the next step is to calculate the switching frequency at the nominal load current using the following formula: fs ( I load ) 2 I load (Vout Vin Vd ) Ip 2 L Where: IP = Peak current as described in the previous peak current control section L = Selected inductor value Iload = Nominal load current Vd = Rectifier diode forward voltage (typically 0.3V) A smaller inductor value gives a higher converter switching frequency, but lowers the efficiency. The inductor value has less effect on the maximum available load current and is only of secondary order. The best way to calculate the maximum available load current under certain operating conditions is to estimate the expected converter efficiency at the maximum load current. This number can be taken out of the efficiency graphs shown in page 6. The maximum load current can then be estimated as follows: I load max Ip 2 L fsmax 2 (Vout Vin) Where: IP = Peak current as described in the previous peak current control section L = Selected inductor value fSmax = Maximum switching frequency as calculated previously η= Expected converter efficiency. Typically 70% to 85% The maximum load current of the converter is the current at the operation point where the converter starts to enter the continuous conduction mode. Usually the converter should always operate in discontinuous conduction mode. ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 10/15 UM1660 Last, the selected inductor should have a saturation current that meets the maximum peak current of the converter (as calculated in the peak current control section). Use the maximum value for ILIM for this calculation. Another important inductor parameter is the dc resistance. The lower the dc resistance, the higher the efficiency of the converter. Setting the Output Voltage The output voltage is calculated as: Vout 1.233V (1 R1 ) R2 For battery powered applications a high impedance voltage divider should be used with a typical value for R2 of 200kΩ and a maximum value for R1 of 2.2MΩ. Smaller values might be used to reduce the noise sensitivity of the feedback pin. A feedforward capacitor across the upper feedback resistor R1 is required to provide sufficient overdrive for the error comparator. The lower the switching frequency of the converter, the larger the feedforward capacitor value required. A good starting point is to use a 10pF feedforward capacitor. As a first estimation, the required value for the feedforward capacitor at the operation point can also be calculated using the following formula: C FF 1 fs 2 R1 20 Where: R1 = Upper resistor of voltage divider fS = Switching frequency of the converter at the nominal load current (See previous section for calculating the switching frequency) CFF = Choose a value that comes closest to the result of the calculation The larger the feedforward capacitor the worse the line regulation of the device. Therefore, when concern for line regulation is paramount, the selected feedforward capacitor should be as small as possible. Output Capacitor Selection The output capacitor limits the output ripple and maintains the output voltage during large load transitions. Ceramic capacitors with X5R or X7R temperature characteristics are highly recommended due to their small size, low ESR, and small temperature coefficients. For most applications, a 1μF ceramic capacitor is sufficient. For some applications a reduction in output voltage ripple can be achieved by increasing the output capacitor. Input Capacitor Selection For good input voltage filtering, low ESR ceramic capacitors are recommended. A 4.7µF ceramic input capacitor is sufficient for most of the applications. For better input voltage filtering this value can be increased. Diode Selection Schottky diode is a good choice for UM1660 because of its low forward voltage drop and fast reverse recovery. Using Schottky diode can get better efficiency. The current rating of the diode should meet the peak current rating of the converter as it is calculated in the peak current control section. Use the maximum value for ILIM for this calculation. ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 11/15 UM1660 Layout Considerations High switching frequencies and relatively large peak currents make the PCB layout a very important part of design. Good design minimizes excessive EMI on the feedback paths and voltage gradients in the ground plane, resulting in a stable and well-regulated output. Good layout for the UM1660 can be implemented by following a few simple design rules. 1. The input capacitor should be placed as close as possible to the input pin for good input voltage filtering. 2. The inductor and diode should be placed as close as possible to the switch pin to minimize the noise coupling into other circuits. 3. The feedback network should be routed away from the inductor. The feedback pin and feedback network should be shielded with a ground plane or trace to minimize noise coupling into this circuit. 4. Wide traces should be used for connections in bold as shown in the Figure below. A star ground connection or ground plane minimizes ground shifts and noise. D1 L1 V IN VIN SW R1 C IN VOUT UM1660 EN CFF COUT FB GND R2 ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 12/15 UM1660 Package Information UM1660S: SOT23-5 Outline Drawing D b θ Symbol 5 E E1 4 2 3 L 1 e c 0.2 e1 A1 Side View A End View A2 Top View A A1 A2 b c D E E1 e e1 L θ DIMENSIONS MILLIMETERS Min Max 1.050 1.250 0.000 0.100 1.050 1.150 0.300 0.500 0.100 0.200 2.820 3.020 1.500 1.700 2.650 2.950 0.950REF 1.800 2.000 0.300 0.600 0° 8° INCHES Min Max 0.041 0.049 0.000 0.004 0.041 0.045 0.012 0.020 0.004 0.008 0.111 0.119 0.059 0.067 0.104 0.116 0.037REF 0.071 0.079 0.012 0.024 0° 8° Land Pattern 2.40 0.90 0.70 0.95 NOTES: 1. Compound dimension: 2.92×1.60; 2. Unit: mm; 3. General tolerance ±0.05mm unless otherwise specified; 4. The layout is just for reference. 0.95 PHO M Tape and Reel Orientation ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 13/15 UM1660 UM1660DA: DFN6 2.0×2.0 A Outline Drawing A3 A1 Side View D D2 D2/2 E2/2 L E E2 R 0.100 b e Symbol A A1 A3 b D E D2 E2 e L DIMENSIONS MILLIMETERS Min Typ 0.57 0.60 0 0.03 0.15TYP 0.20 0.25 1.95 2.00 1.95 2.00 1.45 1.55 0.76 0.86 0.65TYP 0.30 0.35 Max 0.63 0.05 0.30 2.075 2.075 1.65 0.96 0.40 Bottom View 0.65 1.00 1.20 2.50 Land Pattern 0.65 0.25 NOTES: 1. Compound dimension: 2.00×2.00; 2. Unit: mm; 3. General tolerance ±0.05mm unless otherwise specified; 4. The layout is just for reference. Tape and Reel Orientation AAG M ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 14/15 UM1660 IMPORTANT NOTICE The information in this document has been carefully reviewed and is believed to be accurate. Nonetheless, this document is subject to change without notice. Union assumes no responsibility for any inaccuracies that may be contained in this document, and makes no commitment to update or to keep current the contained information, or to notify a person or organization of any update. Union reserves the right to make changes, at any time, in order to improve reliability, function or design and to attempt to supply the best product possible. Union Semiconductor, Inc Add: 2F, No. 3, Lane 647 Songtao Road, Shanghai 201203 Tel: 021-51093966 Fax: 021-51026018 Website: www.union-ic.com ________________________________________________________________________ http://www.union-ic.com Rev.05 Feb.2014 15/15