HT7991 2.5A Peak Current, 1MHz Asynchronous Step-up PWM Converter Features Applications • Input Voltage from 2.6V to 5.5V • All Single Cell Li or Dual Cell Battery Application • Adjustable Output Voltage Up to 12V • Portable Equipment/Handheld Devices • Internal 0.2Ω Low Power Switch • Fixed PWM Switching Frequency: 1MHz General Description • Precision Feedback Reference Voltage: 0.6V (±2%) The HT7991 is a current mode asynchronous stepup DC-DC converter. The fully integrated power MOSFET transistor, with its 0.2Ω drain source resistance, ensures a high level of device power efficiency. A fixed 1MHz switching frequency has been chosen to permit smaller inductors to be used in the application circuit. The error amplifier noninverting input amplifier is connected to an internal precision 0.6V/±2% reference voltage while an integrated soft-start function reduces the inrush current during the converter start up period. The device is available in a SOT23-6 package type. • Ultra Low Shutdown Current: 0.1μA • Embedded Loop Frequency Compensation • Programmable OCP Threshold via External Resistor, ROC • Complete Protections: Soft Start , UVLO, OCP, OTP and OVP • Package Type: SOT23-6 Application Circuit D1 L1: 3.3uH C1: 47uF C2: 0.1uF HT7991 VOUT R2 5 VIN LX 1 4 EN FB 3 6 OC GND 2 C3: 47uF ON OFF R1 VOUT=5.1V 94.0% 92.0% C4: 0.1uF Efficecy (%) VIN=2.6V~4.2V 90.0% 88.0% Vin=3.3V 86.0% Vin=3.7V Vin=4.2V 84.0% ROC 82.0% 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 IOUT (A) Rev. 1.00 1 July 25, 2014 2 HT7991 Block Diagram OC OCP Adjuestment EN Enable Control UVLO VIN OVP PWM Comparator OSC OTP Control Logic LX Slope Compensation PGND GND FB EA 0.6V Soft-start GND Rev. 1.00 2 July 25, 2014 HT7991 Pin Assignment SOT23-6 6 5 4 7991 1 2 Top View 3 Pin Description Pin Order Name Type 1 LX O Power switch output Pin Description 2 GND G Ground terminal 3 FB I Error amplifier inverting input 4 EN I Enable control - High active 5 VIN P Power supply input 6 OC I Adjustment current limit via an external resistor to ground Absolute Maximum Ratings Value Unit VIN Parameter -0.3 to +6 V LX -0.3 to +17 V Other Pins +6 V Power Dissipation 455 mW Maximum Junction Temperature +150 °C -65 to +150 °C +260 °C Human Body Model 2000 V Machine Model 200 V 220 °C/W Value Unit Storage Temperature Range Lead Temperature (Soldering 10sec) ESD Susceptibility Junction-to-Ambient Thermal Resistance, θJA Recommended Operating Range Parameter VIN 2.6 to 5.5 V Operating Temperature Range -40 to +85 °C Note that Absolute Maximum Ratings indicate limitations beyond which damage to the device may occur. Recommended Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specified performance limits. Rev. 1.00 3 July 25, 2014 HT7991 Electrical Characteristics Symbol (VIN=3.3V and TA=+25°C, unless otherwise specified) Parameter Test Condition Min — Typ Max Unit Supply Voltage VIN Input Voltage Range 2.6 — 5.5 V IQ Quiescent Current – Non-switching VFB=0.66V — 210 — μA IIN Supply Current – Switching VFB=0.55V — 1.5 — mA ISHDN Shutdown Current VIN=2.4V, VEN=0V — 0.1 1 μA Boost Converter VOUT Output Voltage Range fSW Switching Frequency VFB=0.5V — Switching Frequency Variation VIN=2.6V to 5.5V DMAX Minimum Duty Cycle RDS Internal Power MOSFET Drain Source Resistance – RDS(ON) ILX=2A ISWL Driver Leakage Current VEN=0V, VLX=12V VFB Feedback Voltage Output Voltage Line Regulation — — VIN=2.6V to 5.5V 3 — 12 V 0.8 1.0 1.2 MHz — 5 — % — 90 — % — 0.2 — Ω μA — 0.1 1 0.588 0.6 0.612 V — 0.2 — %/V VEN EN High Voltage Threshold — 1.2 — — V VEN EN Low Voltage Threshold — — — 0.4 V — 2.2 — V — — 100 — mV Protections VUVLO Input Supply Turn On Voltage Level UVLO+ UVLO Hysteresis IOCP Over Current Protection Threshold OC is floating (default) — 2.5 — A VOVP Output Over Voltage Threshold OVP — — 17 V tOTP Thermal Shutdown Threshold OTP tR Thermal Recovery Temperature Rev. 1.00 — 4 — 150 — °C — 125 — °C July 25, 2014 HT7991 Typical Performance Characteristics VIN=3.3V, VOUT=5V, CIN=22μF+22μF, COUT=22μF+22μF, L=3.3µH, TA=25°C, unless otherwise noted Rev. 1.00 Steady State: IOUT=0A Steady State: VIN=4.2V, IOUT=0A Steady State: IOUT=0.1A Steady State: VIN=4.2V, IOUT=0.1A Steady State: IOUT=1.0A) Steady State: VIN=4.2V, IOUT=1.0A Start Up from VIN: IOUT=0A Start Up from VIN: VIN=4.2V, IOUT=0A 5 July 25, 2014 HT7991 VIN=3.3V, VOUT=5V, CIN=22μF+22μF, COUT=22μF+22μF, L=3.3µH, TA=25°C, unless otherwise noted Start Up from VIN: IOUT=1A Start Up from VIN: VIN=4.2V, IOUT=1A Start Up from EN: IOUT=1A Start Up from EN: VIN=4.2V, IOUT=1A Load Transient: VIN=3.3V, VOUT=5V Load Transient: VIN=3.3V, VOUT=5V Load Transient: VIN=4.2V, VOUT=5V Load Transient: VIN=4.2V, VOUT=5V Rev. 1.00 6 July 25, 2014 HT7991 VIN=3.3V, VOUT=5V, CIN=22μF+22μF, COUT=22μF+22μF, L=3.3µH, TA=25°C, unless otherwise noted VOUT=5.1V 94.0% 90.0% 92.0% 80.0% 70.0% 90.0% Efficecy (%) Efficecy (%) VOUT=5.1V 100.0% 88.0% Vin=3.3V 86.0% 84.0% Vin=3.3V 60.0% Vin=3.7V 50.0% Vin=4.2V 40.0% Vin=3.7V 30.0% Vin=4.2V 20.0% 10.0% 82.0% 0.0% 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 10 20 30 40 IOUT (A) VOUT=5.1V 140 70 80 90 100 Vout=5.1V 91% 90% 120 Vin=3.3V Vin=3.7V Vin=4.2V 100 89% 88% Efficecy (%) Surface Temperature (°C) 60 Efficiency vs. IOUT Efficiency vs. IOUT 80 60 40 20 87% 86% 85% 84% Vin=3.3V 83% Vin=3.7V Vin=4.2V 82% 0 81% 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 -40 -15 10 35 60 85 Room Ambient (°C) IOUT (A) Efficiency vs. TEMP @ IOUT=1A Surface TEMP vs. IOUT Vout=5.1V 1.050 Operation Frequency fsw (MHz) 50 IOUT (mA) 1.020 Vin=3.3V Vin=3.7V 0.990 Vin=4.2V 0.960 0.930 0.900 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 Iout (A) fSW vs. IOUT Rev. 1.00 7 July 25, 2014 HT7991 Functional Description Protections The HT7991 has dedicated protection circuitry running during normal operation to protect the IC. The Soft Start function (SS) is set around 1ms internally to prevent the inrush current during power-on period. The Over Current Protection (OCP) is illustrated in detail below. The Over Temperature Protection (OTP) turns off the power device when the die temperature reaches excessive levels. The Under Voltage LockOut comparator (UVLO) protects the power device during supply power startup and shutdown to prevent operation at voltages less than the minimum input voltage. HT7991 restricts 17V maximum output voltage (OVP) to avoid the burn-out of the internal components and the output devices. Operation The HT7991 is an asynchronous step-up dc/dc converter. With a wide input range from 2.6V to 5.5V, the HT7991 is suitable for portable Li-battery based applications such as power banks. Thanks for the high operation switching frequency, 1MHz, the HT7991 allows the use of small external components while still being able to have low output voltage ripple. The embedded loop frequency compensation circuitry simplifies the system design and reduces the external components. Setting Output Voltage The external resistor divider sets the output voltage (see Typical Application Circuit). The feedback resistor, R1, also sets the feedback loop bandwidth with the internal compensation capacitor. R1 and R2 are calculated in equation: Setting Over Current Threshold Via External Resistor In default, HT7991 sets the maximum peak current passing through the internal power MOSFET restricted to 2.5A when OC pin keeps floating via a resistor. The R OC resistor value is normally set between 19.2kΩ and 30kΩ. The current limit will be set from 1.6A to 2.5A. Do not put the capacitor at this pin. The approximate OCP trip point could be calculated according the equation: R2 = R1 / ((VOUT / 0.6V) – 1) (Ω) Over Current Threshold (A) IOCP = 48000 / ROC (A) 2.5A 1.6A 19.2K 30K External Setting Resistor, ROC (W) Rev. 1.00 8 July 25, 2014 HT7991 Component Selection Guide Diode The breakdown voltage rating of the diode is preferred to be higher than the maximum input voltage. The current rating for the diode should be equal to the maximum output current for best reliability in most applications. In this case, it is possible to use a diode with a lower average current. However the peak current should be higher than the maximum load current. Inductor The selected inductor should have a saturation current that meets the maximum peak current of the converter. Another important inductor parameter is the dc resistance. The lower the dc resistance gains the higher the efficiency of the converter. For most applications, the inductor value can be calculated from the following equation: Input Capacitor Vin 2 (Vout−Vin) L = ( ) × Iripple×fsw Vout A low ESR ceramic capacitor is needed between the VIN pin and GND pin. Use ceramic capacitors with X5R or X7R dielectrics for its low ESR and small temperature coefficients. For most applications, the capacitance in the range of 2.2μF to 10μF capacitor is sufficient. The higher value of ripple current reduces inductance, but the conductance loss, core loss, and current stress of the inductor and switching devices increase. It’s suggested that choosing the inductor ripple current to be 30% of the maximum load current. Output Capacitor The selection of output capacitor is driven by the maximum allowable output voltage ripple. Using ceramic capacitors with X5R or X7R dielectrics for its low ESR characteristic is suggested. The capacitance in the range of 10μF to 100μF is sufficient. Recommended Component Values D1 L1 VIN C2 C1: 16V/0.1uF VOUT C4 C3: 25V/0.1uF HT7991 R2 5 VIN LX 1 4 EN FB 3 6 OC GND 2 ON OFF R1 ROC VOUT (V) R1 (kΩ) R2 (kΩ) C3 (μF) L1 (μH) C4 (μF) 5.1 10 (1%) 75 (1%) 0.1 3.3 47 12.0 10 (1%) 190 (1%) 0.1 6.8 47 Rev. 1.00 9 July 25, 2014 HT7991 Layout Consideration Guide Suggested Layout To reduce problems with conducted noise, PCB layout is very important to stability. The layout recommendations are listed below: (1) The input bypass capacitor must be placed close to the VIN pin. (2) The inductor, schottky diode, and output capacitor trace should be as short as possible to reduce conducted and radiated noise and increase overall efficiency. (3) Keep the power ground and supply paths as short and wide as possible. Thermal Considerations The recommended operating conditions specify a����� ���� maximum junction temperature is 125°C. The junction to ambient thermal resistance, θJA, is layout dependent. On a standard JEDEC 51-7 four-layer thermal test board, the thermal resistance, θJA, of the QFN-10 package is 50°C/W. The maximum power dissipation at TA=25°C can be calculated by the following formula. For continuous operation, do not exceed the absolute maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and the allowed difference between the junction and ambient temperatures. The maximum power dissipation can be calculated by the following formula: PD(MAX) = (125oC – 25oC) / (220oC/W) = 455mW For a fixed TJ(MAX) of 125oC, the maximum power����� ���� dissipation depends on the operating ambient temperature and the package's thermal resistance, θJA. The de-rating curve below shows the effect of rising ambient temperature on the maximum recommended power dissipation. PD(MAX) = (TJ(MAX) – TA) / θJA (W) Maximum Power Dissipation (mW) Where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction to ambient thermal resistance. Rev. 1.00 625 Four-Layer PCB 500 375 250 125 0.0 0 25 50 75 85 100 Ambient Temperature (oC) 10 125 July 25, 2014 HT7991 Package Information Note that the package information provided here is for consultation purposes only. As this information may be updated at regular intervals users are reminded to consult the Holtek website for the latest version of the package information. Additional supplementary information with regard to packaging is listed below. Click on the relevant section to be transferred to the relevant website page. • Further Package Information (include Outline Dimensions, Product Tape and Reel Specifications) • Packing Meterials Information • Carton information Rev. 1.00 11 July 25, 2014 HT7991 6-pin SOT23-6 Outline Dimensions Symbol Nom. Max. A — — 0.057 A1 — — 0.006 A2 0.035 0.045 0.051 b 0.012 — 0.020 C 0.003 — 0.009 D — 0.114 BSC — E — 0.063 BSC — e — 0.037 BSC — e1 — 0.075 BSC — H — 0.110 BSC — L 0.012 0.018 0.024 θ 0° — 8° Symbol Rev. 1.00 Dimensions in inch Min. Dimensions in mm Min. Nom. Max. A — — 1.45 A1 — — 0.15 A2 0.90 1.15 1.30 b 0.30 — 0.50 C 0.08 — 0.22 D — 2.90 BSC — E — 1.60 BSC — e — 0.95 BSC — e1 — 1.90 BSC — H — 2.80 BSC — L 0.30 0.45 0.60 θ 0° — 8° 12 July 25, 2014 HT7991 Copyright© 2014 by HOLTEK SEMICONDUCTOR INC. The information appearing in this Data Sheet is believed to be accurate at the time of publication. However, Holtek assumes no responsibility arising from the use of the specifications described. The applications mentioned herein are used solely for the purpose of illustration and Holtek makes no warranty or representation that such applications will be suitable without further modification, nor recommends the use of its products for application that may present a risk to human life due to malfunction or otherwise. Holtek's products are not authorized for use as critical components in life support devices or systems. Holtek reserves the right to alter its products without prior notification. For the most up-to-date information, please visit our web site at http://www.holtek.com.tw. Rev. 1.00 13 July 25, 2014