RT4805 2.5MHz, Synchronous Boost Regulator with Bypass Mode General Description Features The RT4805 allows systems to take advantage of new battery chemistries that can supply significant energy when the battery voltage is lower than the required voltage for system power ICs. By combining built-in power transistors, synchronous rectification, and low supply current; this IC provides a compact solution for systems using advanced Li-Ion battery chemistries. The RT4805 is available in the WL-CSP-16B 1.67x1.67 (BSC) package. VSEL = L 3.2V VSEL = H 3.4V Maximum Continuous Load Current: 2A at VIN > 2.65V Boosting VOUT to 3.35V Up to 96% Efficient True Bypass Operation when VIN > Target VOUT The RT4805 is a boost regulator designed to provide a minimum output voltage from a single-cell Li-Ion battery, even when the battery voltage is below system minimum. In boost mode, output voltage regulation is guaranteed to a maximum load current of 2A. Quiescent current in Shutdown Mode is less than 1A, which maximizes battery life. The regulator transitions smoothly between Bypass and normal Boost Mode. The device can be forced into Bypass Mode to reduce quiescent current. 4 Few External Components: 0.47H Inductor and 0603 Case Size Input and Output Capacitors Input Voltage Range: 1.8V to 5V Output Range from 2.85V to 4.4V Internal Synchronous Rectifier True Load Disconnect when Shut Down Forced Bypass Mode VSEL Control to Optimize Target VOUT Short-Circuit Protection I2C Controlled Interface Ultra low Operating Quiescent Current Small WL-CSP 16B Package Applications Single-Cell Li-Ion, LiFePO4 Smart-Phones or Tablet 2.5G/3G/4G Mini-Module Data Cards Simplified Application Circuit RT4805 VOUT VIN CIN + - COUT L1 LX To pull high voltage VSEL EN nBYP SDA SCL PGOOD AGND PGND Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT4805 Ordering Information Pin Configurations (TOP VIEW) RT4805 Package Type WSC : WL-CSP-16B 1.67x1.67 (BSC) A1 B1 Note : VSEL Richtek products are : C1 RoHS compliant and compatible with the current Suitable for use in SnPb or Pb-free soldering processes. A3 B2 B3 D1 A4 VIN B4 SCL VOUT VOUT C2 nBYP SDA requirements of IPC/JEDEC J-STD-020. A2 EN PGOOD VIN D2 C3 C4 LX LX D3 D4 AGND PGND PGND PGND WL-CSP-16B 1.67x1.67 (BSC) Marking Information 3X : Product Code W : Date Code 3XW Functional Pin Description Pin No. Pin Name Pin Function A1 EN Enable. When this pin is HIGH, the circuit is enabled. A2 PGOOD Power Good. It is a open-drain output. PGOOD pin pulls low automatically if the overload or OTP event occurs. VIN Input Voltage. Connect to Li-Ion battery input power source. B1 VSEL Output Voltage Select. When boost is running, this pin can be used to select output voltage B2 SCL Serial Interface Clock. (Pull down if I2C is non-used). B3, B4 VOUT Output Voltage. Place COUT as close as possible to the device. C1 nBYP Bypass. This pin can be used to activate Forced Bypass Mode. When this pin is LOW, the bypass switches are turned on and the IC is otherwise inactive. C2 SDA Serial Interface Date Line. (Pull down if I2C is non-used). LX Switching node. Connect to inductor. D1 AGND Analog Ground. This is the signal ground reference for the IC. All voltage levels are measured with respect to this pin. D2, D3, D4 PGND Power Ground. This is the power return for the IC. The COUT bypass capacitor should be returned with the shortest path possible to these pins. A3, A4 C3, C4 Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 Function Block Diagram VIN Current Sense VMIN Control OSC + SCL SDA nBYP VSEL EN PGOOD + Digital Soft-Start Control + + - - VMAX Control LX PSM Control ZCD AGND Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 PWM Logic VOUT Power MOS Control Stage November 2015 PGND is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT4805 Operation RT4805 combined built-in power transistors, synchronous rectification, and low supply current, it provides a compact solution for system using advanced Li-Ion battery chemistries. In boost mode, output voltage regulation is guaranteed to a maximum load current of 2A. Quiescent current in Shutdown mode is less than 1A, which maximizes battery life. Mode Startup and Shutdown State When VIN is rising and through the LIN state, it will enter the Startup state. If EN is pulled low, any function is turned-off in shutdown mode. Soft-Start State It starts to switch in Soft-start state. After the LIN state, output voltage is rising with the internal reference voltage. There is a point, it will go to fault condition, if the large output capacitor is used and the timeout is over 2ms after the soft-start state. Depiction Condition LIN 1 Linear startup 1 VIN > VOUT LIN 2 Linear startup 2 VIN > VOUT Soft-Start Boost soft-start VOUT < VOUT(MIN) Fault State Boost Boost mode VOUT = VOUT(MIN) Bypass Bypass mode VIN > VOUT(MIN) As the Figure 1 shown, it will enter to the Fault state as below, LIN LIN State When VIN is rising, it enters the LIN State. There are two parts for the LIN state. It provides maximum current for 1A to charge the COUT in LIN1, and the other one is for 2A in LIN2. By the way, the EN is pulled high and VIN > UVLO. As the figure shown, if the timeout is over the specification, it will enter the Fault mode. EN = 1, Vin > UVLO The timeout of LIN2 is over the 1024s. It is over the 2ms when the state changed from Soft-start state to Boost mode. It will be the high impedance between the input and output when the fault is triggered. A restart will be start after 1ms. Boost Mode There are two normal operation modes, one is the Boost mode, and the other one is Bypass mode. In the Boost mode, it provides the power to load by internal synchronous switches after the soft-start state. LIN 1 Timeout < 512μs Bypass Mode Timeout > 512μs Soft-Start Timeout < 1024μs Timeout > 2ms Timeout < 2ms LIN 2 Timeout > 1024μs Fault State Boost mode Figure 1. RT4805 State Chart Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 In Bypass mode, output voltage will increase with VIN when input voltage is rising after the soft-start state. Bypass Mode Operation In automatic mode, it transits from Boost mode to Bypass mode. As the Figure 2 shown, there are three MOSFET (Q1 to Q3). The Q1 & Q2 is for Boost mode, it is used by Q3 for Bypass mode. VOUT will be followed the VIN when VIN is higher than the target output voltage. As the Figure 3 shown, it is transited by bypass MOSFET (Q3). VOUT followed the VIN. is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 VOUT PGOOD (Power Good) Q3 Power good is a open-drain input. If it is 0, it stands for fault occurred. The power good provide the information to show the state of the system, Q1 VIN PGOOD pin show high when the sequence of soft-start is completed. Any fault cause PGOOD to be pulled low. PGOOD low when PMOS current limit has triggered for OR the die the temperature exceeds 120C. PGOOD is re-asserted when the device cools below to 100C. LX Q2 GND Figure 2. Boost Converter With Bypass Mode OCP VOUT The converter senses the current signal when the VIN high-side P-MOSFET turns on. As a result, the OCP is cycle by-cycle current limitation. If the OCP occurs, the converter holds off the next on pulse until inductor current drops below the OCP limit. OTP The converter has an over-temperature protection. When the junction temperature is higher than the thermal shutdown rising threshold, the system will be Figure 3. RT4805 mode changed latched and the output voltage will no longer be regulated until the junction temperature drops under the Force Pass-Through Mode falling threshold. When EN pulled high and nBYP pulled low. The device is active in the Force pass-through mode. It supplies EN & nBYP current is approximately 15A typ. From the battery, the device is short circuit protected by a current limit of 4000mA. It is used to select mode. As the table 1 shown, there are four device states. When EN and nBYP both pull high, RT4805 is normal operation and enter automatic mode. VSEL It is concerned the minimum output voltage at the heavy load condition. There are two output voltage levels (3.2V & 3.4V) in Boost mode and Bypass mode. It can be selected by VSET, so it must not be floating. Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 If the EN pull low, and nBYP pull high/low, RT4805 is forced in shut-down mode and the quiescent is less than 1A. It works in force pass-through mode, if the EN set high and nBYP set low. is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT4805 Table 1 EN input nBYP input Device State 0 0/1 The device is shut down in pass-through mode featuring a shutdown current down to ca. 1A typ. 1 0 The device is active in forced pass-through mode. The device supply current is approximately 15A typ. From the battery. The device is short circuit protected by a current limit of ca. 4000mA. 1 1 The device is active in auto mode (dc/dc boost, pass-through mode) The device supply current is approximately 55A typ. from the battery Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 Absolute Maximum Ratings (Note 1) VIN, VOUT to AGND ---------------------------------------------------------------------------------------- 0.2V to 6V EN, VSEL, PGOOD, nBYP to AGND ------------------------------------------------------------------ 0.2V to 6V LX ---------------------------------------------------------------------------------------------------------------- (PGND 0.2V) to 6V Power Dissipation, PD @ TA = 25C WL-CSP-16B 1.67x1.67 (BSC) --------------------------------------------------------------------------- 2.09W Package Thermal Resistance (Note 2) WL-CSP-16B 1.67x1.67 (BSC), JA --------------------------------------------------------------------- 47.7C/W Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------- 260C Junction Temperature --------------------------------------------------------------------------------------- 150C Storage Temperature Range ------------------------------------------------------------------------------ 65C to 150C ESD Susceptibility (Note 3) HBM (Human Body Model) -------------------------------------------------------------------------------- 2kV MM (Machine Model) ---------------------------------------------------------------------------------------- 200V CDM (Charge Device Model)------------------------------------------------------------------------------ 1kV Recommended Operating Conditions (Note 4) Input Voltage Range --------------------------------------------------------------------------------------- 1.8V to 5V Output Voltage Range ------------------------------------------------------------------------------------- 2.85V to 4.4V Ambient Temperature Range------------------------------------------------------------------------------ 40C to 85C Junction Temperature Range ----------------------------------------------------------------------------- 40C to 125C Electrical Characteristics (VIN = 3V, VOUT = 3.4V, TA = 25C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit 1.8 -- 5 V VIN Operation Range VIN VIN Quiescent Current IQ Auto Bypass Mode, VIN = 3.8V -- 35 70 A VIN Quiescent Current IQ Boost mode, ILOAD = 0mA, Switching, VIN = 3V -- 55 100 A VIN Quiescent Current IQ Force Bypass without LIQ, VIN = 3.6V -- 15 25 A VIN Shutdown Current ISHDN EN = 0V, VIN = 3.6V -- -- 1 A VOUT to VIN Reverse Leakage ILK VOUT = 5V, EN = nBYP = H, VIN < VOUT -- 0.2 1 A VOUT Leakage Current ILK_OUT VOUT = 0V, EN = 0V, VIN = 4.2V -- 0.1 1 A Under Voltage Lock Out VUVLO VIN Rising -- 1.6 1.8 V Under Voltage Lock Out Hysteresis VUVLO_HYS -- 200 -- mV PGOOD Low PGOOD Leakage Current Logic Level High EN, VSEL, nBYP, SCL, SDA VPGOOD IPGOOD = 5mA -- -- 0.4 V IPGOOD _LK VPGOOD = 5V -- -- 1 A 1.2 -- -- V VIH Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT4805 Parameter Symbol Test Conditions Min Typ Max Unit -- -- 0.4 V Logic Level Low EN, VSEL, nBYP, SCL, SDA VIL Output Voltage Accuracy VREG VOUT VIN > 100mV, PWM 2 -- 2 % Minimum On Time TON VIN = 3V, VOUT = 3.5V, ILOAD > 1000mA -- 80 -- ns Maximum Duty Cycle DMAX 40 -- -- % Switching Frequency FSW VIN = 2.65V, VOUT = 3.5V, ILOAD = 1000mA 2 2.5 3 MHz Boost Valley Current Limit ICL VIN = 2.9V 3.5 4 4.5 A Soft-Start Input Current Limit ISS_PK LIN1 -- 1000 -- mA Soft-Start Input Current Limit ISS_PK LIN2 -- 2000 -- mA Pass Through Mode Current Limit IBPCL VIN = 3.2V -- 4 -- A N-Channel Boost Switch RDS(ON) RDSN VIN = 3.2V, VOUT = 3.5V -- 60 95 m P-Channel Boost Switch RDS(ON) RDSP VIN = 3.2V, VOUT = 3.5V -- 40 80 m N-Channel Bypass Switch RDS(ON) RDSP_BYP VIN = 3.2V, VOUT = 3.5V -- 40 60 m Hot Die Trigger Threshold THD -- 100 -- o -- o Hot Die Release Threshold THDR -- 90 C C Over Temperature Protection TOTP -- 160 -- o Over Temperature Protection Hysteresis TOTP_HYS -- 20 -- o FAULT Restart Time TRST -- 1 -- ms C C Note 1. Stresses beyond those listed “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 in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability. Note 2. JA is measured at TA = 25C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. Note 3. Devices are ESD sensitive. Handling precaution recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 Typical Application Circuit RT4805 A3 + - CIN 10μF L1 0.47μH To pull high voltage 1k 1k VOUT VIN B3, B4 COUT 22μF x 2 C3, C4 LX B1 VSEL A1 EN C1 nBYP C2 SDA B2 SCL To pull high voltage 1M PGOOD A2 AGND PGND D1 D2, D3, D4 BOM of Test Board Reference Description Manufacturer Package Parameter Typ. Unit CIN 10F/16V/X5R Taiyo : EMK212ABJ106KG 0805 C 10 F COUT 22F/10V/X5R Taiyo : LMK212BBJ226MG 0805 C 22 F L1 0.47μH, 20% TOKO : DFE2520F-R47M 2520 L 0.47 H DCR (Series R) 29 m Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT4805 Typical Operating Characteristics Efficiency vs. Load Current Efficiency vs. Load Current 100 95 95 VIN = 2.5V 90 Efficiency (%) Efficiency (%) 100 VIN = 2.7V 85 VIN = 3V VIN = 3.3V 80 VIN = 2.5V 90 VIN = 2.7V VIN = 3V 85 VIN = 3.3V 80 75 75 VOUT = 3.4V, ILOAD = 100mA to 2A VOUT = 3.4V, ILOAD = 1mA to 2A 70 70 0.001 0.01 0.1 1 0.1 10 1 Load Current (A) Efficiency vs. Load Current 100 95 95 Efficiency (%) Efficiency (%) Efficiency vs. Load Current 100 90 VIN = 2.5V VIN = 2.7V 85 10 Load Current (A) VIN = 3V 80 VIN = 2.5V 90 VIN = 2.7V VIN = 3V 85 80 75 75 VOUT = 3.2V, ILOAD = 100mA to 2A VOUT = 3.2V, ILOAD = 1mA to 2A 70 70 0.001 0.01 0.1 1 0.1 10 1 Load Current (A) 10 Load Current (A) Output Regulation vs. Load Current Output Regulation vs. Load Current 0.03 0.03 VIN = 2.8V Output Regulation (%) Output Regulation (%) VIN = 2.5V 0.02 VIN = 3V VIN = 3.3V 0.01 0 -0.01 0.02 0.01 0 VIN = 2.5V VIN = 2.8V -0.01 VIN = 3V VOUT = 3.2V, ILOAD = 0A to 2A VOUT = 3.4V, ILOAD = 0A to 2A -0.02 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Load Current (A) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 -0.02 2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Load Current (A) is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 Output Ripple vs. Load Current Output Ripple vs. Load Current 70 70 VOUT = 3.4V, ILOAD = 0A to 2A VOUT = 3.2V, ILOAD = 0A to 2A 60 Output Rippie (mV) Output Rippie (mV) 60 50 VIN = 2.5V 40 VIN = 2.7V 30 VIN = 3V VIN = 3.3V 20 10 50 40 VIN = 2.7V 30 VIN = 3V 20 VIN = 3.1V 10 0 0 0 500 1000 1500 2000 0 500 1000 1500 2000 Load Current (mA) Load Current (mA) Maximum Load Current vs. Input Voltage Startup 5.0 Maximum Load Current (A)1 VIN = 2.5V 4.0 3.0 VOUT (2V/Div) 2.0 ILX (1A/Div) 1.0 EN (5V/Div) PGOOD (5V/Div) VIN = 2.5V to 3.7V, V OUT = 3.4V 0.0 2.5 2.7 2.9 3.1 3.3 3.5 3.7 Time (100s/Div) Input Voltage (V) Startup VIN = 3V, VOUT = 3.2V, Load = 50 VIN = 3V, VOUT = 3.4V, Load = 50 Overload Protection VOUT (2V/Div) VIN = 3V, VOUT = 3.4V VOUT (2V/Div) ILX (1A/Div) ILX (2A/Div) EN (5V/Div) PGOOD (5V/Div) PGOOD (5V/Div) Time (100s/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 Time (1ms/Div) is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT4805 Load Transient Overload Protection VOUT (200mV/Div) VOUT (2V/Div) ILX (2A/Div) PGOOD (5V/Div) IOUT (200mA/Div) VIN = 3V, VOUT = 3.4V, ILOAD = 100mA to 500mA VIN = 3V, VOUT = 3.2V Time (1ms/Div) Time (25s/Div) Load Transient Transient Overload VOUT (200mV/Div) VOUT (500mV/Div) VIN = 3V, VOUT = 3.4V, ILOAD = 1A to 3.8A IOUT (200mA/Div) IOUT (2A/Div) VIN = 3V, VOUT = 3.2V, ILOAD = 100mA to 500mA Time (25s/Div) PGOOD (5V/Div) Time (50s/Div) Transient Overload VOUT (500mV/Div) VIN = 3V, VOUT = 3.2V, ILOAD = 1A to 3.8A IOUT (2A/Div) PGOOD (5V/Div) Time (50s/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 Application Information restarts if the input voltage recovers to the input Enable voltage UVLO high level. The device can be enabled or disabled by the EN pin. When the EN pin is higher than the threshold of logic-high, the device starts operating with soft-start. Once the EN pin is set at low, the device will be shut down. In shutdown mode, the converter stops switching, internal control circuitry is turned off, and the load is disconnected from the input. This also means that the output voltage can drop below the input voltage during shutdown. Thermal Shutdown The device has a built-in temperature sensor which monitors the internal junction temperature. If the temperature exceeds the threshold, the device stops operating. As soon as the IC temperature has decreased below the threshold with a hysteresis, it starts operating again. The built-in hysteresis is designed to avoid unstable operation at IC temperatures near the over temperature threshold. Soft-Start State After the successful completion of the LIN state (VOUT ≥ VIN 300mV). During Soft-Start state, VOUT is ramped up by Boost internal loop. If VOUT fails to reach target value during the Soft-Start period for more than 2ms, a fault condition is declared. Inductor Selection The recommended nominal inductance value is 1.5H. It is recommended to use inductor with dc saturation current ≥ 3500mA Input Capacitor Selection Output Voltage Setting User can select the output voltage level by VSEL and I2C. If the VSEL pulled low, the default is 3.2V, and if it pulled high, the default is 3.4V. The output voltage range is from 2.85V to 4.4V. At least a 10F input capacitor is recommended to improve transient behavior of the regulator and EMI behavior of the total power supply circuit for LX. And at least a 1F ceramic capacitor placed as close as possible to the VIN and GND pins of the IC is recommended. Power Save Mode PSM is the way to improve efficiency at light load. When the output voltage is lower than a set threshold voltage, the converter will operate in PSM. Output Capacitor Selection At least 22F x 2 capacitors is recommended to improve VOUT ripple. It raises the output voltage with several pulses until the loop exits PSM. Output voltage ripple is inversely proportional to COUT. Under-Voltage Lockout Output capacitor is selected according to output ripple which is calculated as : The under-voltage lockout circuit prevents the device from operating incorrectly at low input voltages. It prevents the converter from turning on the power switches under undefined conditions and prevents the battery from deep discharge. VIN voltage must be greater than 1.7V to enable the converter. During operation, if VIN voltage drops below 1.6V, the converter is disabled until the supply exceeds the UVLO rising threshold. The RT4805 automatically Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 VRIPPLE(P P) tON and ILOAD COUT V tON tSW D tSW 1 IN V OUT therefore : V ILOAD COUT tSW 1 IN VOUT VRIPPLE(P P) and 1 tSW fSW is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT4805 The maximum VRIPPLE occurs when VIN is at minimum and ILOAD is at maximum. Output Discharge Function With the EN pin set to low, the VOUT pin is internally connected to GND by an internal discharge N-MOSFET switch. This feature prevents residual charge voltages on capacitor connected to VOUT pins, which may impact proper power up of the system. Current Limit RT4805 employs a valley-current limit detection scheme to sense inductor current during the off-time. When the loading current is increased such that the loading is above the valley current limit threshold, the off-time is increased until the current is decreased to valley-current threshold. Next on-time begins after current is decreased to valley-current threshold. On-time is decided by (VOUT VIN) / VOUT ratio. The output voltage decreases when further loading current increase. As the following figure shown, the current limit function is implemented by the scheme. IIN (DC) Valley Current Limit f Inductor Current IIN (DC) DIL DIL = VIN D L f Figure 4. Inductor Currents In Current Limit Operation Protection The RT4805 features some protections, such as OCP, OVP, UVP and OTP. As the table shown, it is described the protection actions. Protection Type Threshold Refer to Electrical Spec. Protection Method Shut Down Delay Time Reset Method OCP IL > 4A Turn on UG until IL < 4A 2ms After FAULT 1ms OVP VIN > 6V Turn off UG, LG, BYP_MOS No delay VIN < 5.7V UVP VIN <1.6V Turn off UG, LG, BYP_MOS No delay VIN>1.7V OTP TEMP > 160oC Turn off UG, LG, BYP_MOS No delay OTP Hysteresis = 20oC Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 14 is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 Register Table Lists [Slave address = 1110101 (0x75)] Name Address Description CONFIG 0x01 MODE control & Spread modulation control VOUTFLOOR 0x02 Output Voltage Selection VOUTROOF 0x03 Output Voltage Selection ILIMSET 0x04 Set current limit & Soft-start current limit STATUS 0x05 Read IC status I2C Interface The RT4805 I2C slave address is 1110101 (7bits). The I2C interface supports fast mode (bit rate up to 400kb/s). The write or read bit stream (N 1) is shown below : Read N bytes S Slave Address 0 A Register Address A Sr Assume Address = m R/W MSB Data 2 Slave Address 1 A MSB Data 1 LSB A Data for Address = m LSB A Data for Address = m+1 MSB Data N LSB A P Data for Address = m + N - 1 Write N bytes S Slave Address 0 A R/W Register Address Assume Address = m A MSB Data 1 Data for Address = m MSB LSB A MSB Data 2 Data for Address = m + 1 Data N LSB A LSB A P Data for Address = m + N - 1 Driven by Master, Driven by Slave (RT4805), P Stop, Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 S Start, Sr Repeat Start is a registered trademark of Richtek Technology Corporation. www.richtek.com 15 RT4805 Offset 0x01 CONFIG Bits 7 6 Name RESET Reset 0 0 Type RW RW 5 4 3 2 RESERVED RESERVED SSFM 0 0 0 0 0 1 RW RW RW RW RW RW ENABLE<1> ENABLE<0> Offset 0x02 Bits 7 1 0 MODE_CTRL MODE_CTRL <1> <0> VOUTFLOOR 6 5 Name RESERVED RESERVED RESERVED 4 3 2 1 0 VSEL<4> VSEL<3> VSEL<2> VSEL<1> VSEL<0> Reset 0 0 0 0 0 1 1 1 Type RW RW RW RW RW RW RW RW Offset 0x03 Bits 7 VOUTROOF 6 5 Name RESERVED RESERVED RESERVED 4 3 2 1 0 VSEL<4> VSEL<3> VSEL<2> VSEL<1> VSEL<0> Reset 0 0 0 0 1 0 1 1 Type RW RW RW RW RW RW RW RW Offset 0x04 Bits 7 ILIMSET 6 Name RESERVED RESERVED 5 4 3 2 1 0 ILIM_OFF SOFT_START ILIM<3> ILIM<2> ILIM<1> ILIM<0> Reset 0 0 0 1 1 1 0 1 Type RW RW RW RW RW RW RW RW Offset 0x05 STATUS Bits 7 6 5 4 3 2 1 0 Name TSD HOTDIE DCDCMODE OPMODE ILIMPT ILIMBST FAULT PGOOD Reset 0 0 0 0 0 0 0 0 Type RO RO RO RO RO RO RO RO Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 16 is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 Name Function Addr CONFIG MODE control & Spread modulation control 0x01 name Reset Bit Mode 7 R/W RESET Description 0 0 : Disable ID detection function 1 : Enable ID detection function 00 : Device operation follows hardware control signal (refer to table 1) 01 : Device operation in auto transition mode (boost/bypass) regardless of the nBYP control signal (EN = 1) 10 : Device is forced in pass-through mode regardless of the nBYP control signal (EN = 1) 11 : Device is in shutdown mode. The output voltage is reduced to a minimum value (VIN VOUT 3.6V) regardless of the nBYP control signal (EN = 1) [6 : 5] R/W ENABLE[1 : 0] 0 4 R/W Reserved 0 3 R/W Reserved 0 2 R/W SSFM 0 0 : Spread spectrum modulation is disabled. 1 : Spread spectrum modulation is enabled in PWM mode. MODE_CTRL[1 : 0] 01 00 : Device operation follows hardware control signal. 01 : PFM with automatic transition into PWM operation. 10 : Forced PWM operation. 11 : PFM with automatic transition into PWM operation (VSEL = L), forced PWM operation (VSEL = H). Name Function Addr VOUTFLOOR Output Voltage Selection 0x02 name Reset [1 : 0] R/W Bit Mode [7 : 5] R/W [4 : 0] R/W Reserved VOUT[4 : 0] 000 00000 : VOUT = 2.85V 00001 : VOUT = 2.9V 00010 : VOUT = 2.95V 00011 : VOUT = 3V 00111 00100 : VOUT = 3.05V … 00111 : VOUT = 3.2V (default) … 11111 : VOUT = 4.4V Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 Description is a registered trademark of Richtek Technology Corporation. www.richtek.com 17 RT4805 Name Function Addr VOUTROOF Output Voltage Selection 0x03 name Reset Bit Mode [7 : 5] R/W [4 : 0] R/W Reserved VOUT[4 : 0] Description 000 00000 : VOUT = 2.85V 00001 : VOUT = 2.9V 00010 : VOUT = 2.95V 00011 : VOUT = 3V 01011 00100 : VOUT = 3.05V … 01011 : VOUT = 3.4V (default) … 11111 : VOUT = 4.4V Name Function Addr ILIMSET Set current limit & Softstart current limit 0x04 name Reset Bit Mode [7 : 6] R/W Reserved 00 5 R/W ILIM_OFF 0 0 : Current Limit Enabled 1 : Current Limit Disabled 4 R/W Soft-Start 1 0 : Boost soft-start current is limited per ILIM bit settings 1 : Boost soft-start current is limited to ca. 1250mA inductor valley current [3 : 0] R/W ILIM[3 : 0] 1101 Description 1000 : 1500mA 1001 : 2000mA 1010 : 2500mA 1011 : 3000mA 1100 : 3500mA 1101 : 4000mA (default) 1110 : 4500mA 1111 : 5000mA Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 18 is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 Name Function Addr STATUS Read IC status 0x05 name Reset Bit Mode Description 7 R TSD 0 0 : Normal operation. 1 : Thermal shutdown tripped. The flag is reset after readout. 6 R HOTDIE 0 0 : TJ < 115°C. 1 : TJ > 115°C. 5 R DCDCMODE 0 0 : Device operates in PFM mode. 1 : Device operates in PWM mode. 4 R OPMODE 0 0 : Device operates in pass-through mode. 1 : Device operates in dc/dc mode. 3 R ILIMPT 0 0 : Normal operation. 1 : Indicates that the bypass FET current limit has triggered. This flag is reset after readout. 2 R ILIMBST 0 0 : Normal operation. 1 : Indicates that the average input current limit has triggered for 1.5ms in dc/dc boost mode. This flag is reset after readout. 1 R FAULT 0 0 : Normal operation. 1 : Indicates that a fault condition has occurred. This flag is reset after readout. 0 R PGOOD 0 0 : Indicates the output voltage is out of regulation. 1 : Indicates the output voltage is within its nominal range. This bit is set if the converter is forced in pass-through mode. Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 19 RT4805 Thermal Considerations Layout Consideration For continuous operation, do not exceed absolute The PCB layout is an important step to maintain the high performance of RT4805. maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and difference between junction and ambient temperature. The maximum power dissipation can be calculated by the following formula : PD(MAX) = (TJ(MAX) TA) / JA where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and JA is the junction to ambient thermal resistance. For recommended operating condition specifications, the maximum junction temperature is 125C. The junction to ambient thermal resistance, JA, is layout dependent. For WL-CSP-16B 1.67x1.67 (BSC) package, the thermal resistance, JA, is 47.7 on a standard JEDEC 51-7 four-layer thermal test board. Both the high current and the fast switching nodes demand full attention to the PCB layout to save the robustness of the RT4805 through the PCB layout. Improper layout might show the symptoms of poor line or load regulation, ground and output voltage shifts, stability issues, unsatisfying EMI behavior or worsened efficiency. For the best performance of the RT4805, the following PCB layout guidelines must be strictly followed. Place the input and output capacitors as close as possible to the input and output pins respectively for good filtering. For thermal consider, it needed to maximize the pure area for the power stage area besides the LX. The maximum power dissipation at TA = 25C can be calculated by the following formula : PD(MAX) = (125C 25C) / (47.7) = 2.09W for WL-CSP-16B 1.67x1.67 (BSC) package The maximum power dissipation depends on the operating ambient temperature for fixed TJ(MAX) and thermal resistance, JA. The derating curve in Figure 5 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. Maximum Power Dissipation (W)1 2.5 Four-Layer PCB 2.0 1.5 1.0 0.5 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 5. Derating Curve of Maximum Power Dissipation Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 20 is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015 RT4805 LX L A3 A4 B1 B2 B3 B4 C1 C2 C3 C4 D1 D2 D3 D4 COUT A2 COUT CIN A1 COUT VOUT VIN GND Figure 6. PCB Layout Guide Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS4805-00 November 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 21 RT4805 Outline Dimension Dimensions In Millimeters Symbol Dimensions In Inches Min. Max. Min. Max. A 0.500 0.600 0.020 0.024 A1 0.170 0.230 0.007 0.009 b 0.240 0.300 0.009 0.012 D 1.620 1.720 0.064 0.068 D1 E 1.200 1.620 0.047 1.720 0.064 0.068 E1 1.200 0.047 e 0.400 0.016 WL-CSP-16B 1.67x1.67 (BSC) Richtek Technology Corporation 14F, No. 8, Tai Yuen 1st Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is bel ieved to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries. Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 22 is a registered trademark of Richtek Technology Corporation. DS4805-00 November 2015