HT7936A

HT7936A/HT7936B White LED Step-up Charge Pump Converter Features · Input voltage range: 2.8V to VOUT · Oscillator frequency: 1MHz · Driving current: 110mA (HT7936A), · Soft start function, current limit, 150mA (HT7936B) short circuit protection · Fixed output voltage: 5V (HT7936A), · Small outline 6-pin SOT23 package 4.5V (HT7936B) Applications · Cellular phones · Handheld devices · PDAs · White LED display backlighting · DSCs General Description during device power on. The operating voltage range is from 2.8V to the full output voltage value, VOUT. The HT7936A and HT7936B are charge-pump type DC-DC step-up converter devices, which can generate regulated fixed output voltages of 5.0V and 4.5V. Their high degree of functional integration requires only the addition of three external capacitors, namely a flying capacitor and an input and output capacitor, to implement a full step-up conversion function. To meet the demands of today¢s power sensitive applications, the devices, have a very low standby current value as well as the extra safety features of current limit and short circuit protection. This range of device features, supplied in 6-pin SOT23 package type, will ensure that these device will find excellent use in a wide range of DC-DC step-up converter applications. The devices have the additional benefit of an integrated soft start function to reduce the level of in-rush current Selection Table Part No. Output Voltage Tolerance Package Marking HT7936A 5.0V ±4% SOT23-6 936A HT7936B 4.5V ±4% SOT23-6 936B Rev 1.40 1 August 4, 2018 HT7936A/HT7936B Block Diagram C + V IN M 4 C - M 1 M 2 M 3 S h o r t C ir c u it P r o te c io n V O U T C o n tro l G N D E N V R E F 1 M H z O S C N o te : D u r in g o p e r a tio n th e fo llo w in g s e q u e n c e o c c u r s : 1 . M 1 , M 3 O n / M 2 , M 4 O ff 2 . M 2 , M 4 O n / M 1 , M 3 O ff Pin Assignment S O T 2 3 -6 C + 6 V IN 5 C 4 9 3 6 x 1 2 3 V O U T G N D E N T o p V ie w " x " s ta n d s fo r "A " o r "B " Pin Description Pin No. Pin Name Description 1 VOUT Regulated Output Voltage. VOUT should be bypassed with a 1mF to 10mF low ESR ceramic capacitor placed as close as possible to the pin for best performance. 2 GND Ground. This pin is the voltage reference for the regulator output voltage. 3 EN Device On/Off Control 1: Enable 0: Disable Pin must not be left floating. 4 C- Capacitor Negative Pin. Flying capacitor negative terminal. 5 VIN Input Supply Voltage. VIN should be bypassed with a 1mF to 10mF low ESR ceramic capacitor. 6 C+ Capacitor Positive Pin. Flying capacitor positive terminal. Rev 1.40 2 August 4, 2018 HT7936A/HT7936B Absolute Maximum Ratings Input Supply Voltage..................................................6V Other Pins Voltage ....................................................6V Operating Temperature Range ...............-40°C to 85°C Maximum Junction Temperature..........................125°C Note: These are stress ratings only. Stresses exceeding the range specified under ²Absolute Maximum Ratings² may cause substantial damage to the device. Functional operation of this device at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability. Electrical Characteristics Symbol VIN VIN=VEN=3.7V, CIN=CPUMP=COUT=1mF, Ta=25°C, unless otherwise specified. Parameter Test Conditions Min. Typ. Max. Unit HT7936A 2.8 ¾ 5.0 V HT7936B 2.8 ¾ 4.5 V HT7936A, VIN>3.2V, IO£110mA 4.80 ¾ 5.20 V HT7936B, VIN>3.2V, IO£140mA 4.32 ¾ 4.68 V Input Supply Voltage VOUT Output Voltage ISHDN Shutdown Current VEN=0 ¾ 0.1 1.0 mA IQ Operation Current ¾ ¾ 2.0 4.0 mA IO HT7936A 110 ¾ ¾ mA Output Current HT7936B 150 ¾ ¾ mA ISHORT Short Circuit Current ¾ ¾ 60 90 mA ILIMIT Current Limit ¾ ¾ 370 500 mA fOSC Switching Frequency ¾ 0.8 1.0 1.3 MHz VENH EN Pin Voltage High 2.8V £ VIN £ 5.0V 1.5 ¾ ¾ V VENL EN Pin Voltage Low 2.8V £ VIN £ 5.0V ¾ ¾ 0.4 V VRIPPLE Output Ripple Voltage IO=60mA, COUT=2.2mF ¾ 30 ¾ mV h HT7936A, VIN=3.0V, IO=50mA ¾ 80 ¾ % Efficiency HT7936B, VIN=2.8V, IO=70mA ¾ 80 ¾ % Note: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. The guaranteed specifications apply only for the test conditions listed. Specifications are production tested at Ta=25°C. Specifications over -40°C to +85°C operating temperature range are assured by design. Rev 1.40 3 August 4, 2018 HT7936A/HT7936B Functional Description Capacitor Selection These DC-DC step-up converters can generate fixed level output voltages higher than their input supply voltage. Careful selection of the three external capacitors CIN, COUT and CPUMP is important because they will affect ramp-up time, output ripple and transient performance. Optimum performance will be obtained when low ESR (