1/4 STRUCTURE Silicon Monolithic Integrated Circuit PRODUCT NAME 1ch DC／DC Converter Controller IC with Built-in Synchronous Rectifier TYPE BD9121GUL FEATURES ・Output Voltage：Fixed(1.2V, 1.3V, 1.4V), Output Current：0.3A ・Fast transient response with current mode PWM control system ・High efficiency with synchronous rectifier ○ABSOLUTE MAXIMUM RATING（Ta=25℃） Parameter Symbol VCC Supply Voltage PVCC SEL Voltage SEL SW・ITH Voltage SW, ITH SW Output Current ISW Power Dissipation 1 Pd1 Operating Temperature Range Topr Storage Temperature Range Tstg Maximum Junction Temperature Tjmax Limit -0.3～+7 *1 -0.3～+7 *1 -0.3～+7 -0.3～+7 0.5 *1 660 *2 -25～+85 -55～+150 +150 Unit V V V V A mW ℃ ℃ ℃ 1 * Pd, ASO, and Tjmax=150℃ should not be exceeded. 2 * Derating is 5.28mW/℃ for temperatures above Ta=25℃ (when mounted on 50mm×58mm×1.6mm glass epoxy PCB). ○OPERATING CONDITIONS（Ta=-25～+85℃） Parameter Symbol VCC Supply Voltage PVCC SW Average Output Current ISW Min. 2.55 2.55 - 3 * Pd and ASO should not be exceeded. REV. A Typ. 3 3 - Max. 3.6 3.6 0.3*3 Unit V V A 2/4 ○ ELECTRICAL CHARACTERISTICS (Unless otherwise specified, Ta=25℃, VCC=PVCC=3V, VOUT=1.3V） Parameter Symbol Limit Unit Condition Min. Typ. Max. ICC - 400 640 μA Output Voltage1 VOUT1 -2 - +2 % Output Voltage2 VOUT2 -3 - +3 % Oscillation Frequency1 FOSC1 2.4 3 3.6 MHz Oscillation Frequency2 FOSC2 2.1 3 3.9 MHz Pch FET ON Resistance RONP - 0.3 0.6 Ω PVCC=3V Nch FET ON Resistance RONN - 0.2 0.4 Ω PVCC=3V ITH Sink Current ITHSI 10 20 - μA VOUT=2V, SEL=OPEN VOUT=0.8V, SEL=OPEN Bias Current Ta=-25～85℃ Ta=25～85℃ ITHSO 10 20 - μA UVLO Threshold Voltage VUVLO1 2.1 2.25 2.4 V VCC=3→0V UVLO Release Voltage VUVLO2 2.12 2.3 2.5 V VCC=0→3V TSS 25 50 100 μs TLATCH 0.68 1.36 2.72 ms VSCP - 0.65 1 V ITH Source Current Soft Start Time Timer Latch Time Output Short circuit Threshold Voltage ○PHYSICAL DIMENSION SCP/TSD Operational Mode VOUT=1.3→0V, SEL=OPEN ○BLOCK DIAGRAM・APPLICATION CIRCUIT VCC VREF PVCC 9121 Current Comp + R Q S Lot No. SEL Gm Amp SLOPE Current Sense/ Protect 4.7μF + L CLK OSC + VCC 10Ω Driver Logic SW 4.7μF Soft Start UVLO TSD PGND SCP GND VOUT ITH RITH CITH VCSP50L2 (UNIT:mm) REV. A 0.1μF 3V Input Output 3/4 ○PIN DISTRIBUTION [Bottom View] B1 B2 SW A1 B3 PVCC A2 PGND B4 VCC A3 GND VOUT A4 SEL ○SETTING THE OUTPUT VOLTAGE ITH ○PIN No.・PIN NAME SEL Output Voltage〔V〕 PIN No. PIN NAME GND 1.2 A1 PGND OPEN 1.3 A2 GND VCC 1.4 A3 SEL A4 ITH B1 SW B2 PVCC B3 VCC B4 VOUT ※Cannot switch in operational mode. REV. A 4/4 ○NOTES FOR USE (1) Absolute maximum rating Although the quality of this IC is rigorously controlled and will function properly in normal operating conditions, the IC may be destroyed when applied voltage or operating temperature exceeds its absolute maximum rating. Because short mode or open mode cannot be specified when the IC is destroyed, it is important to take physical safety measures such as fusing if a special mode in excess of absolute rating limits is to be implemented. (2) GND potential Make sure the potential for the GND pin is always kept at the minimum, regardless of the operating mode. In addition, verify that the GND voltage is lower than the potential of all terminals except SW, PGND and GND in all conditions, including electric transient events. (3) Thermal design Do not exceed the power dissipation (Pd) of the package specification rating under actual operation. Provide sufficient margin in the thermal design to account for the Pd expected in actual use. (4) Short-circuits between pins and incorrect mounting position When mounting the IC onto the set PCB, be extremely careful about the orientation and position of the IC. The IC may be destroyed if it is incorrectly positioned for mounting. Do not short-circuit between pins, or between a pin and the power supply or ground terminal. Note that introducing foreign matter in these paths will cause shorts and may damage the IC. (5) Operation in strong electromagnetic fields Use in strong electromagnetic fields may cause malfunctions. Use extreme caution with electromagnetic fields. (6) ASO (Area of Safe Operation) Do not exceed the maximum ASO parameter or the absolute maximum ratings of the output driver. (7) TSD (Thermal Shutdown) circuit This product is provided with a built-in thermal shutdown (TSD) circuit, which is activated when the IC chip temperature rises to the threshold value. In this case, TSD automatically latches output OFF. Output is restored when UVLO is deactivated. Note that the TSD circuit is provided for the exclusive purpose shutting down the IC in the presence of extreme heat, and is not designed to protect the IC per se or guarantee performance when or after extreme heat conditions occur. Therefore, do not operate the IC with the expectation of continued use or subsequent operation once the TSD is activated. (8) GND wiring pattern When both a small-signal GND and high current GND are present, single-point grounding (at the standard point on the circuit set board) is recommended. This will separate the small-signal and high current patterns, and serves to ensure that the high current flow and wire impedance will not change the small-signal GND voltage. In the same way, care must be taken to avoid wiring pattern fluctuations in any connected external component GND. (9) Operation in supply voltage range Circuit functionality is guaranteed within the operating ambient temperature, as long as the operation is within the supply voltage range. The standard electrical characteristics cannot be guaranteed. However, any variation in these values will be small, as long as the operation is within the supply voltage range. (10) The application schematic presented above is an example of recommended circuit layout. Although the circuit example is sound, actual circuit characteristics should be checked carefully before use. Be sure to allow sufficient margins to accommodate variations between external devices and this IC when employing the depicted circuit with other circuit constants modified. Both static and transient characteristics should be considered in establishing these margins. When switching noise is substantial and may impact the system, a low pass filter should be inserted between the Vcc and PVcc pins, and a Schottky barrier diode established between the SW and PGND pins. (11) Overcurrent protection circuit/Output short protection circuit The overcurrent protection circuit is built into output, and functions as the current limit. Note that if the protection circuit operates more than a specified time period (when the output short-circuit protection circuit detects a load short or other similar state) the output will be latched OFF. Output is restored when UVLO is deactivated. Although the protection circuits effectively prevent IC destruction under fault conditions, they should not be employed continuously. REV. A Notice Notes No copying or reproduction of this document, in part or in whole, is permitted without the consent of ROHM Co.,Ltd. The content specified herein is subject to change for improvement without notice. The content specified herein is for the purpose of introducing ROHM's products (hereinafter "Products"). If you wish to use any such Product, please be sure to refer to the specifications, which can be obtained from ROHM upon request. Examples of application circuits, circuit constants and any other information contained herein illustrate the standard usage and operations of the Products. The peripheral conditions must be taken into account when designing circuits for mass production. Great care was taken in ensuring the accuracy of the information specified in this document. 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