Freescale Semiconductor Application Note AN3809 Rev. 1.0, 12/2008 Powering the i.MX27 with the 5 Channel MC34704B IC 1 Overview This document presents an analysis of the possibility to use the 5 Channel MC34704B power management IC to supply a system based on i.MX27. The focus was done on i.MX27 itself, considering its needs in terms of voltage, current and power up sequence. The needs to supply the DDR and Flash memories were also taken into account. 2 Scope Contents 1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 i.MX27 Power Requirements . . . . . . . . . . . . . . . . . . 2 4 MC34704B 5 Ch. DC/DC Power Management IC . . 3 5 Software Considerations . . . . . . . . . . . . . . . . . . . . . 8 6 Component Selection . . . . . . . . . . . . . . . . . . . . . . . 9 7 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8 Layout Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 9 Layout Considerations . . . . . . . . . . . . . . . . . . . . . 17 10 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . 18 With the info presented here, the i.MX27 can be supplied so it will work on a basic application on which low power modes can not be accessed due to the absence of power gating system on the MC34704B. To be able to use low power modes, extra circuitry must be added to the system. © Freescale Semiconductor, Inc., 2008. All rights reserved.. All rights reserved. i.MX27 Power Requirements 3 i.MX27 Power Requirements i.MX27 Power Signal Symbol Min. Typ Max Units Core Voltage Supply (@266MHz) QVDD 1.2 1.3 1.52 V Core Voltage Supply (@400MHz) QVDD 1.38 1.45 1.52 V RTC, SCC, Separate Supply Voltage RTCVDD 1.2 - 1.52 V Analog Supply Voltage: FPMVDD, UPLLVDD, MPLLVDD VDD 1.35 1.4 1.6 V OSC32VDD VOSC32 1.1 - 1.6 V I/O Supply Voltage, Fast (7, 11, 12, 14, 15) NVDD_FAST 1.75 - 2.8 V I/O Supply Voltage, Slow (5, 6, 8, 9, 10, 13, AVDD) NVDD_SLOW 1.75 - 3.05 V OSC26VDD VOSC26 2.68 - 2.875 V I/O Supply Voltage, DDR (1, 2, 3, 4) NVDD_DDR 1.75 - 1.9 V Fuse box read Supply Voltage FUSE_VDD 1.7 1.875 1.95 V Fuse box Program Supply Voltage FUSE_VDD 3 3.15 3.3 V 3.1 i.MX27 Power Up Sequence The i.MX27/MX27L processor consists of three major sets for power supply voltage named QVDD (core logic supply), FUSEVDD (analog supply for FUSEBOX), and NVDDVDDA (IO supply). The External Voltage Regulators and power-on devices must provide the applications processor with a specific sequence of power and resets to ensure proper operation. It is important that the applications processor power supplies be powered-up in a certain order to avoid unintentional fuse blown. QVDD should be powered up before FUSEVDD. If the core operating frequency is set to 266MHZ and VDDQ supply group is required to be 1.3V, then, an extra voltage rail is needed to provide the Analog supply Voltage. Otherwise, if Core supply voltage can be set higher or operating frequency is 400MHz core supply and Analog supply can be sourced from a single power supply at a typical value of 1.45V. Noticed that since the maximum operating voltage for the Core voltage group is 1.52V, caution must be taken in order to have a very tight regulation and avoid overstressing or blowing the microprocessor terminals. Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 2 Freescale Semiconductor MC34704B 5 Ch. DC/DC Power Management IC 4 MC34704B 5 Ch. DC/DC Power Management IC The MC34704B is a multi-channel Power Management IC (PMIC) used to address power management needs for various multimedia application microprocessors. Its ability to provide 5 independent output voltages with a single input power supply (2.7 and 5.5V) together with its high efficiency, make it ideal for portable devices powered up by Li-Ion/polymer batteries or for USB powered devices as well. The MC34704B is housed in a 7x7mm, Pb-free, QFN56 and is capable of operating at a switching frequency of up to 2MHz. This makes it possible to reduce external component size and to implement full space efficient power management solutions. Features • • • • • • • • • • • 4.1 5 DC/DC (MC34704B) switching regulators with up to ±2% output voltage accuracy Dynamic voltage scaling on all regulators Selectable voltage mode control or current mode control on REG8 I2C programmability Output under-voltage and over-voltage detection for each regulator Over-current limit detection and short-circuit protection for each regulator Thermal limit detection for each regulator Integrated compensation for REG3 and REG8 5µA maximum shutdown current (All regulators are off, 5.5V VIN) True cutoff on all of the boost and buck-boost regulators Pb-free packaging designated by suffix code EP MC34704B Capabilities MC34704B Capabilities Regulator Output Voltage (V) Output Current (mA) Min. Typ Max Typ Max Reg2 0.6 2.8/3.3 3.6 200 500 Reg3 0.6 1.2/1.5/1.8 1.8 150 550 Reg4 0.6 1.8/2.5 3.6 100 300 Reg5 0.6 3.3 3.6 150 550 Reg8 5 15 15 15 30 Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 Freescale Semiconductor 3 MC34704B 5 Ch. DC/DC Power Management IC 4.2 Interface Diagram The diagram below shows how the communication pins and power sources must be connected to the i.MX27, and the output voltage for which each one must be configured. It is a good practice to place ferrite beads on the REG2 voltage supply in order to avoid noise caused for supplying three different voltage domains in the i.MX27: i.MX27 MC34704B QVDD REG3 (1.5V) RTCVDD, OSC32VDD, UPLLVDD, FPMVDD, MPLLVDD REG2 (2.8V) Ferrite Beads REG4 (1.8V) NVDD5, 6, 8, 9, 10, 13, AVDD NVDD7, 11, 12, 14, 15 REG5 (3.3V) OSC26VDD REG8 NVDD1-4 N/C REG2 FUSE_VDD 4.7K SCL I2C_CLK_PD18 REG2 4.7K SDA I2C_DAT A_ PD17 REG2 10K RST POR Figure 1. Interface Diagram As can be seen, REG8 of MC34704B is available to supply other peripherals or external circuitry that may require 5 to 15V at 30mA. RST signal on the MC34704B goes low as soon as regulators 2, 3 and 4 have reached a stable state at their final value. This indicates the i.MX27 that all the voltages are ready for it to start operating. When this signal goes low, the i.MX27 restarts all the modules and peripherals to a known state so the system can start its operation. I2C communication is established through pins SCL and SDA of the MC34704B, which have to be connected to I2C_CLK_PD18 and I2C_DATA_PD17 of the i.MX27 respectively. Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 4 Freescale Semiconductor MC34704B 5 Ch. DC/DC Power Management IC 4.3 Power Sequencing The MC34704B turns on its regulators following this sequence: • • • REG3 REG2 REG4 Each of the regulators has a soft start time given by a voltage applied to the SS pin. For this application, a 8ms soft start has to be used, for which a resistor divider must be placed from VDDI to ground, as shown in the following picture. Figure 2. Resistor Divider Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 Freescale Semiconductor 5 MC34704B 5 Ch. DC/DC Power Management IC This is how the startup sequence looks like on the MC34704B: Figure 3. Sequencing 1 Figure 4. Sequencing 2 Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 6 Freescale Semiconductor MC34704B 5 Ch. DC/DC Power Management IC The following flow diagram shows how the power pins of the i.MX27 will be turned on according to the power on sequence of the MC34704B. REG3 QVDD, RTCVDD, OSC32VDD, UPLLVDD, FPMVDD, MPLLVDD REG2 NVDD_SLOW, AVDD NVDD_FAST, OSC26VDD REG4 NVDD_DDR REG5 FUSEVDD Figure 5. Flow Diagram Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 Freescale Semiconductor 7 Software Considerations 5 Software Considerations The MC34704B is programmed through a plain I2C protocol, the I.MX processor should include a firmware driver to translate the controlling instructions into I2C commands to allow register writing and flag reading for communication acknowledge. Such driver structure is not defined in this document, instead, it will be discussed only the software portion concerning the MC34704B As well as the I2C commands needed to interact with the MC34704B. The Power on process is very straight forward: • • • If there is a battery insertion, REG3, 2 and 4 will turn on in that order enabling I2C communication protocol as well as i.MX processor power on sequence; in such case, the MC34704B will set the COLDF flag to acknowledge that power on was a result of battery insertion. During the power on process, the MPU should acknowledge that power up was a result of a battery insertion and then send an ALLOFF I2C command to disable the power supply and shut down until a desired hardware Power on is present. If the ON/OFF terminal sees a falling edge, then the MC34704B start a power on cycle ramping up regulator 3, 2 and 4. In this case, the COLDF bit is not set high, thus, when the i.MX processor read this register it acknowledge it is an actual power up and start a full power on sequence. By this time, PMIC is providing 1.45V, 1.8V and 2.7V, and the processor can provide following configuration commands: • REG2, REG3, REG4 OV/UV response • REG5 OV/UV response • REG5 Soft start timing (if desired) At this point the processor can send a REG5 ON/OFF instruction via I2C when the 3.15V rail is required. From now on, all voltage rails can be dynamically scaled up or down using the DVS register and processor can send a power off command when required. Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 8 Freescale Semiconductor Component Selection 6 6.1 Component Selection Inductors VG serves as internal supply for all gate drivers within the MC34704B, L1 dimensions depends directly on the inductance value and the saturation current ISAT, chose and inductor with inductance value between 2.2 to 4.7uH, and ISAT around 150mA. To select Inductors L2 - L5, choose inductance values between 3.0 to 4.7uH, with an ISAT of approximately twice the maximum current to be demanded from each regulator. As approximate values, the regulators will be supplying: Regulator Current (mA) Reg2 30 Reg3 400 Reg4 60 Reg5 60 Note: make sure to use power inductor and not choke inductors for these components to assure correct performance of the MC34704B. 6.2 Capacitors and Resistors Choose capacitors with at least twice the voltage rating as the maximum voltage that the capacitor will be exposed to. for the output inductors, use capacitance values from 10 to 22uF. Resistors are very straight forward to choose, the only important thing while calculating the output voltage of each regulator, is to take the resistor accuracy into consideration specially on those voltage rails where the output voltage is close to the maximum voltage rating of the I.MX terminal; a miscalculation of the resistor accuracy may cause the output voltage to go slightly above the maximum allowed overstressing or damaging the processor terminal in the application. Use 1% or smaller tolerance resistors to have a good control of output voltage values. Note: for more details on external component calculation, please refer to the MC34704B data sheet that can be found at www.freecale.com. Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 Freescale Semiconductor 9 Schematic Schematic VOUT5 = 3.3 V @ 500 mA max VOUT2 = 2.7 V @ 500 mA max VOUT5 VOUT2 68K R240 R64 R81 68K C176 130PF R61 C170 2.55K L10 4.7UH R83 C114 1.0UF C177 22UF GND R239 19.6K GND 1 60.4K L7 4.7UH C103 1.0UF R238 4.3K C165 22UF 2 GND 150PF 1 15K 2 7 C118 1.0UF C232 C231 R241 73.2K 68PF 1000PF C109 GND 1.0UF VOUT4 = 1.8 V @ 300 mA max VCC VOUT4 VCC 11 VCC 1 12 13 L8 4.7UH 43 COMP2 45 46 44 FB2 BT2D PVIN2 48 47 SW2D 49 SW2U VOUT2 51 52 53 50 SW5U VOUT5 SW5D BT5D PVIN5 54 56 FB4 NC8 COMP4 NC7 BT3 NC6 PVIN3 NC5 SW3 NC4 VOUT3 NC3 FB3 NC2 PGND R82 10K 42 41 VDDI 40 39 38 VCC 37 C117 1.0UF C120 36 1.0UF 35 34 GND GND GND 33 32 31 30 29 57 28 27 26 25 24 23 22 21 20 19 18 MC34704BEP C167 22UF 17 VOUT3 16 VOUT3 = 1.45 V @ 550 mA max 15 2 SS 14 NC9 NC1 0.01uF BT4U RST 10 AGND SDA GND VIN SW4U SCL 9 C166 VOUT4 BT1 8 C172 0.01uF 150PF VDDI NC0 7 C173 LION SW4D VG 2 6 BT2U PVIN4 SW1 5 VCC R62 470K ONOFF SWBL L9 4.7UH R77 82K R53 34K BT4D VOUTBL 4 BT5U BTBL 3 0.01uF 1 130PF GND 2 VCC FBBL C171 FB5 1 C169 COMP5 R242 68K R47 2.55K FREQ C168 22UF 55 VCC U13 R71 68K GND VOUT2 R79 GND 22K 10K R235 R234 VDDI 10K POR R60 45.3K GND VOUT2 VIN FILTERING AND DECOUPLING VCC 1 1 GND R68 4.7K R80 4.7K I2C_DATA 2 GND L6 3.3UH D10 MBR230LSFT1G 2 C121 22UF I2C_CLK I2C LINES FOR MC34704 PMIC CONTROL C101 1.0UF Figure 6. MC34704B Schematic Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 10 Freescale Semiconductor Layout Example 8 Layout Example The following is an example of a layout for the MC34704B proposed to work with the I.MX27 Microprocessor, total area is not 100% optimized in order to show the output voltage rails and the communication lines on the power management solution. Freescale proposed layout is designed in 4 layers, using top and bottom layer for routing and component placing and Inner1 and Inner2 layers for Power and Ground respectively. In this document only Top and Bottom layers are presented, since the inner layers are full planes as described above. Figure 7. Top Copper Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 Freescale Semiconductor 11 Layout Example Figure 8. Top Silk Screen Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 12 Freescale Semiconductor Layout Example Figure 9. Top Copper and Silk Screen Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 Freescale Semiconductor 13 Layout Example Figure 10. Bottom Copper Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 14 Freescale Semiconductor Layout Example Figure 11. Bottom Silk Screen. Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 Freescale Semiconductor 15 Layout Example Figure 12. Bottom Copper and Silk Screen. Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 16 Freescale Semiconductor Layout Considerations 9 Layout Considerations • • • • • • • Create a Ground plane layer and tie it to ground signals with vias Place Test vias as close as possible to the IC to ensure a good measurement value PVIN, VIN, VOUT signals have to be tracked with a widely and straight copper area Never trace the Feedback signal in parallel to the SW signal Ensure the SW Inductor is placed as close as possible to its pads SW track has to be as thin and short as possible Make sure the I/O connectors are capable to manage the Load current Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 Freescale Semiconductor 17 Revision History 10 Revision History Revision 1.0 Date 12/2008 Description Of Changes • Initial Release Powering the i.MX27 with the 5 Channel MC34704B IC, Rev. 1.0 18 Freescale Semiconductor How to Reach Us: Home Page: www.freescale.com Web Support: http://www.freescale.com/support USA/Europe or Locations Not Listed: Freescale Semiconductor, Inc. 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