RT9996 Power Management IC for SSD General Description Features The RT9996 is a 2-CH PMIC for SSD (Solid-State Drive). It integrates synchronous buck converters and one voltage detector. z The RT9996 provides 2 independent enable pins for sequence control and auto discharge when powered off on the power line of a NAND Flash. The frequency can be up to 2MHz, allowing the use of smaller sized inductors to meet the space and height limit in handheld applications. To maximize power utilization, the RT9996 is designed with extremely low quiescent current. The buck converter can consume down to 70μA when operating in standby mode. z z z Supply Input Voltage Range : 2.8V to 5.5V Buck 1 / Buck 2 ` Adjustable Output Voltage for VCORE or DRAM Cache ` Output Current up to 1A Voltage Detector ` Programmable Threshold Voltage ` Open-Drain Reset Output RoHS Compliant and Halogen Free Applications z z z 1.8/2.5 inch Solid-State Drives Portable Devices USB-Based Hand-Held Products The RT9996 is available in a VQFN-32L 5x5 package. Pin Configurations Ordering Information NC NC NC NC FB2 EN2 VIN LX2 (TOP VIEW) RT9996 Package Type QV : VQFN-32L 5x5 (V-Type) Note : Richtek products are : ` RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. Marking Information RT9996GQV : Product Number RT9996 GQV YMDNN 1 24 2 23 3 22 4 5 21 GND 20 6 19 7 18 33 8 17 LX2 GND GND VIN VIN GND GND LX1 9 10 11 12 13 14 15 16 NC RESET VDET GND FB1 EN1 VIN LX1 Lead Plating System G : Green (Halogen Free and Pb Free) 32 31 30 29 28 27 26 25 NC NC NC NC NC VIN NC NC VQFN-32L 5x5 YMDNN : Date Code DS9996-01 April 2011 www.richtek.com 1 RT9996 Typical Application Circuit RT9996 VIN 5V 6, 15, 20, 21, 26 VIN LX1 16, 17 L1 2.2µH C1 R1 30k R7 FB1 11 VDET C2 10µF VOUT1 1.2V/1A 13 R2 64.9k R8 VDD 3.3V R9 43k Chip Enable 10 LX2 RESET 24, 25 L2 2.2µH R3 80k 14 EN1 27 EN2 FB2 C3 10µF VOUT2 1.8V/1A 28 R4 64.9k 12, 18, 19, 22, 23, 33 (Exposed Pad) GND Function Block Diagram RESET - VDET 0.7V + VIN EN1 Buck Converter 1 LX1 FB1 VIN EN2 GND www.richtek.com 2 Buck Converter 2 LX2 FB2 DS9996-01 April 2011 RT9996 Functional Pin Description Pin No. 1, 2, 3, 4, 5, 7, 8, 9, 29, 30, 31, 32 6, 15, 20, 21, 26 10 Pin Name Pin Function NC No Internal Connection. VIN Buck Converter 1 and Buck Converter 2 Power Supply Input. RESET Reset Output. 11 VDET 12, 18, 19, 22, 23, GND 33 (Exposed Pad) 13 FB1 Threshold Voltage Detect Setting. Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Buck Converter 1 Feedback Input. 14 EN1 Buck Converter 1 Chip Enable (Active High). 16, 17 LX1 Buck Converter 1 Switch Output (inductor connection point). 24, 25 LX2 Buck Converter 2 Switch Output (inductor connection point). 27 EN2 Buck Converter 2 Chip Enable (Active High). 28 FB2 Buck Converter 2 Feedback Input. DS9996-01 April 2011 www.richtek.com 3 RT9996 Absolute Maximum Ratings z z z z z z z z z (Note 1) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------LX Pin Voltage ------------------------------------------------------------------------------------------------------Other Pins Voltage ------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C VQFN-32L 5x5 -----------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) VQFN-32L 5x5, θJA ------------------------------------------------------------------------------------------------VQFN-32L 5x5, θJC -----------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------Junction Temperature ---------------------------------------------------------------------------------------------Storage Temperature Range ------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Mode) --------------------------------------------------------------------------------------MM (Machine Mode) ----------------------------------------------------------------------------------------------- Recommended Operating Conditions z z z –0.3V to 6.5V –0.3V to (VIN + 0.3V) –0.3V to 6.5V 2.778W 36°C/W 6°C/W 260°C 150°C –65°C to 150°C 2kV 200V (Note 4) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------- 2.8V to 5.5V Junction Temperature Range ------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range ------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 5V, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit Buck Converter 1 Quiescent Current IQ No Load, No Switching -- 70 -- μA Shutdown Current ISHDN EN = GND -- 0.2 -- μA Feedback Reference Voltage VFB -- 0.8 -- V Adjustable Output Voltage VOUT VFB -- VIN−0.2 V -- 0.05 -- %/V -- 0.5 -- %/A VIN Rising 2.1 2.3 2.5 Hysteresis 0.1 0.2 0.3 Output Voltage Line Regulation Output Voltage Load Regulation UVLO Under voltage Lockout Threshold VUVLO V Logic-High VIH 1.5 -- VIN Logic- Low VIL -- -- 0.4 Peak Current Limit ILIM 1.2 -- -- A Oscillator Frequency fOSC 1.2 1.5 1.8 MHz -- 250 -- μs -- 250 -- mΩ -- 260 -- mΩ EN1 Threshold Voltage Start-Up Time VIN = 3.6V, IOUT = 300mA I OUT = 0mA. Time from active EN to 90% of VOUT VIN = VGS = 3.6V, PWM Mode P-MOSFET On-Resistance RDS(ON)_P N-MOSFET On-Resistance RDS(ON)_N VIN = VGS = 3.6V, PWM Mode V To be continued www.richtek.com 4 DS9996-01 April 2011 RT9996 Parameter Symbol Test Conditions Min Typ Max Unit Buck Converter 2 Quiescent Current IQ No Load, No Switching -- 70 -- μA Shutdown Current ISHDN EN = GND -- 0.2 -- μA Feedback Reference Voltage VFB 0.784 0.8 0.816 V Adjustable Output Voltage VOUT VFB -- VIN−0.2 V -- 0.04 -- %/V -- 0.5 -- %/A VIN Rising -- 2.1 -- Hysteresis -- 0.1 -- Output Voltage Line Regulation Output Voltage Load Regulation UVLO Under voltage Lockout threshold VUVLO V Logic-High VIH 1.5 -- VIN V Logic- Low VIL -- -- 0.4 V Peak Current Limit I LIM 1.3 1.7 -- A Oscillator Frequency fOSC VIN = 3.6V, IOUT = 300mA 1.2 1.5 1.8 MHz -- 250 -- μs P-MOSFET On-Resistance RDS(ON)_P IOUT = 0mA Time from active EN to 90% of VOUT VIN = VGS = 3.6V, PWM Mode -- 250 -- mΩ N-MOSFET On-Resistance RDS(ON)_N VIN = VGS = 3.6V, PWM Mode -- 260 -- mΩ VIN Rising (L to H) 0.693 0.7 0.707 VIN Falling (H to L) 0.673 0.68 0.687 VDelay (L to H) 70 100 130 ms VDelay (H to L) 5 10 20 μs EN2 Threshold Voltage Start-Up Time Voltage Detector Voltage Detection Threshold Voltage Detection Delay Time V Thermal Protections Thermal Shutdown Threshold TSD -- 160 -- °C Thermal Shutdown Hysteresis ΔTSD -- 25 -- °C Note 1. Stresses listed as the above “Absolute Maximum Ratings” may cause permanent damage to the device. These are for stress ratings. 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 for extended periods may remain possibility to affect device reliability. Note 2. θJA is measured in natural convection at TA = 25°C on a high-effective thermal conductivity four-layer test board of JEDEC 51-7 thermal measurement standard. The measurement case position of θJ is on the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. DS9996-01 April 2011 www.richtek.com 5 RT9996 Typical Operating Characteristics Buck1 Output Accuracy vs. Load Current Buck1 Efficiency vs. Load Current 100 Output Voltage Accuracy (%) 0.6% 0.6 Efficiency (%) 90 VIN1 = 2.8V VIN1 = 3.6V VIN1 = 4.2V 80 70 60 50 40 VBUCK1 = 1.2V 30 0.001 0.01 0.1 0.4% 0.4 0.2% 0.2 0 0.0% -0.2 -0.2% -0.4 -0.4% -0.6 -0.6% 0.001 0.001 1 Output Voltage Accuracy (%) Efficiency (%) 1 0.6% 0.6 90 VIN2 = 2.8V VIN2 = 3.6V VIN2 = 4.2V 70 60 50 40 VBUCK2 = 1.8V 0.01 0.1 1 0.4% 0.4 0.2 0.2% 0 0.0% -0.2 -0.2% -0.4 -0.4% VBUCK2 = 1.8V, VIN2 = 5V -0.6 -0.6% 0.001 0.001 0.01 0.1 Load Current (A) Load Current (V) Buck1 Output Ripple Buck2 Output Ripple VLX1 (5V/Div) VLX2 (5V/Div) VOUT1 (20mV/Div) VOUT2 (20mV/Div) ILX1 (1A/Div) ILX2 (1A/Div) VIN1 = 5V, ILOAD = 1A Time (500ns/Div) www.richtek.com 6 0.1 Buck2 Output Accuracy vs. Load Current Buck2 Efficiency vs. Load Current 100 30 0.001 0.01 Load Current (A) Load Current (A) 80 VBUCK1 = 1.2V, VIN1 = 5V 1 VIN2 = 5V, ILOAD = 1A Time (500ns/Div) DS9996-01 April 2011 RT9996 Buck1 Load Transient Response VBUCK1 (100mV/Div) IOUT (200mA/Div) VBUCK2 (100mV/Div) ILOAD = 40mA to 0.7A Time (50μs/Div) DS9996-01 April 2011 Buck2 Load Transient Response IOUT (200mA/Div) ILOAD = 40mA to 0.7A Time (50μs/Div) www.richtek.com 7 RT9996 Application Information The basic RT9996 application circuit is shown in the section Typical Application Circuit. External component selection is determined by the maximum load current and begins with the selection of the inductor value and operating frequency followed by CIN and COUT. loop is stable. Loop stability can be checked by viewing the load transient response as described in a later section. Inductor Selection The output ripple is the highest at the maximum input voltage since ΔIL increases with input voltage. Multiple capacitors placed in parallel may be needed to meet the ESR and RMS current handling requirements. Dry tantalum, special polymer, aluminum electrolytic and ceramic capacitors are all available in surface mount packages. Special polymer capacitors offer very low ESR, but have lower capacitance density than other types. Tantalum capacitors have the highest capacitance density, but it is important to only use types that have been surge tested for use in switching power supplies. Aluminum electrolytic capacitors have significantly higher ESR, but can be used in cost-sensitive applications provided that consideration is given to ripple current ratings and long term reliability. Ceramic capacitors have excellent low ESR characteristics but can have a high voltage coefficient and audible piezoelectric effects. The high Q of ceramic capacitors with trace inductance can also lead to significant ringing. For a given input and output voltage, the inductor value and operating frequency determine the ripple current. The ripple current ΔIL increases with higher VIN and decreases with higher inductance, as shown in equation below : ⎤ ⎡V ⎤ ⎡ V ΔIL = ⎢ OUT ⎥ × ⎢1− OUT ⎥ VIN ⎦ ⎣ f ×L ⎦ ⎣ where f is the operating frequency and L is the inductance. Having a lower ripple current reduces not only the ESR losses in the output capacitors, but also the output voltage ripple. Higher operating frequency combined with smaller ripple current is necessary to achieve high efficiency. This, however, requires a large inductor. A reasonable starting point for selecting the ripple current is ΔIL = 0.4I(MAX). The largest ripple current occurs at the highest VIN. To guarantee that the ripple current stays below a specified maximum, the inductor value should be chosen according to the following equation : ⎡ VOUT ⎤ ⎡ VOUT ⎤ L=⎢ ⎥ × ⎢1− ⎥ ⎢⎣ f × ΔIL(MAX) ⎥⎦ ⎢⎣ VIN(MAX) ⎥⎦ CIN and COUT Selection The input capacitance, C IN, is needed to filter the trapezoidal current at the source of the high side MOSFET. To prevent large ripple voltage, a low ESR input capacitor sized for the maximum RMS current should be used. RMS current is given by : V VIN IRMS = IOUT(MAX) × OUT × −1 VIN VOUT This formula has a maximum at VIN = 2VOUT, where IRMS = IOUT(MAX) / 2. Several capacitors may also be paralleled to meet size or height requirements in the design. The selection of COUT is determined by the effective series resistance (ESR) that is required to minimize voltage ripple and load step transients, as well as the amount of bulk capacitance that is necessary to ensure that the control www.richtek.com 8 The output ripple, ΔVOUT, is determined by : ⎡ ⎤ 1 ΔVOUT ≤ ΔIL × ⎢ESR + ⎥ 8fC OUT ⎦ ⎣ Using Ceramic Input and Output Capacitors Higher values, lower cost ceramic capacitors are now becoming available in smaller case sizes. Their high ripple current, high voltage rating and low ESR make them ideal for switching regulator applications. However, care must be taken when these capacitors are used at the input and output. When a ceramic capacitor is used at the input and the power is supplied by a wall adapter through long wires, a load step at the output can induce ringing at the input, VIN. At best, this ringing can couple to the output and be mistakened as loop instability. At worst, a sudden inrush of current through the long wires can potentially cause a voltage spike at VIN large enough to damage the part. Output Voltage Programming The resistive divider allows the FB pin to sense a fraction of the output voltage as shown below DS9996-01 April 2011 RT9996 Voltage Detector RT9996 LX VOUT R1 FB R2 RESET is an open drain output that indicates whether the VDET voltage is higher than 0.7V or not. RESET is typically pulled up to 3.3V. VDET monitors the input voltage and triggers the RESET output (Figure 1). GND For adjustable voltage mode, the output voltage is set by an external resistive divider according to the following equation : VOUT = VFB × ⎛⎜ 1+ R1 ⎞⎟ ⎝ R2 ⎠ RESET is high impedance when the voltage from VDET exceeds the rising threshold 0.7V (typ.). RESET is low when the voltage from VDET falls below the low-battery falling threshold 0.68V (typ.) (Figure 2). If the voltage detector feature is not required, connect RESET to ground and connect VDET to VIN. 3.3V where VFB is the internal reference voltage 0.8V (typ.). Checking Transient Response The regulator loop response can be checked by looking at the load transient response. Switching regulators take several cycles to respond to a step in load current. When a load step occurs, VOUT immediately shifts by an amount equal to ΔILOAD (ESR), where ESR is the effective series resistance of COUT. ΔILOAD also begins to charge or discharge COUT generating a feedback error signal used by the regulator to return VOUT to its steady-state value. RESET Table 1. The RT9996 Power Terminology Buck 1 ON VIN > EN1 > 1.5V 5.5V > VIN > 2.1V DS9996-01 April 2011 VDET 0.7V RESET Delay If the EN pin for the selected buck is pulled high and the input voltage is greater than the under voltage lockout threshold, the selected buck will be turned on. Buck1 can be turned on/off by the external EN1 pin; Buck2 can be turned on/off by the external EN2 pin; Buck3 can be turned on/off by the external EN3 pin. Default Output Voltage - VDET Chip Enable Operation Output State EN UVLO 0.7V Figure 1. VDET and RESET Circuit 0.68V During this recovery time, VOUT can be monitored for overshoot or ringing which would indicate a stability problem. + Buck 2 ON VIN > EN2 > 1.5V 5.5V > VIN > 2.1V R1 ⎞ VOUT = VFB × ⎛⎜ 1 + ⎟ ⎝ R2 ⎠ VFB = 0.8V Figure 2. VDET and RESET Comparator Waveform Choosing the Inductor The RT9996 includes a current-reversal comparator which monitors inductor current and disables the synchronous rectifier as current approaches zero. This comparator will minimize the effect of current reversal for higher efficiency. For some low inductance values, however, the inductor current may still reverse slightly. This value depends on the speed of the comparator in relation to the slope of the current waveform, given by VL / L. VL is the voltage across the inductor (approximately −VOUT) and L is the inductance value. An inductance value of 2.2μH is a good starting value. As the inductance is reduced from this value, the RT9996 will enter discontinuous conduction mode at progressively www.richtek.com 9 RT9996 higher loads. Ripple at VOUT will increase directly proportionally to the magnitude of inductor ripple. Transient response, however, will improve. A smaller inductor changes its current more quickly for a given voltage drive than a larger inductor, resulting in faster transient response. A larger inductor will reduce output ripple and current ripple, but at the expense of reduced transient performance and a physically larger inductor package size. For this reason a larger CVOUT will be required for larger inductor sizes. The input regulator has an instantaneous peak current clamp to prevent the inductor from saturating during transient load or start-up conditions. The clamp is designed so that it does not interfere with normal operation at high loads and reasonable inductor ripple. It is intended to prevent inductor current runaway in case of a shorted output. The DC winding resistance and AC core losses of the inductor will also affect efficiency, and therefore available output power. These effects are difficult to characterize and vary by application. Some inductors and capacitors that may be suitable for this application are listed in Table below : Table 2 Length (mm) Max. VLF5012ST-1R0N2R5 5 VLF5014ST-2R2M2R3 5 VLF3010A-1 3 VLF3012A 3 VLS2010E 2.1 VLS2012E 2.1 NR6045T1R0N 6 CB2016T2R2M 2.2 NR6020T2R2N 6 NR3015 3 LPS4018 3.9 D53LC 5 DB318C 3.8 WE-TPC Type M1 4.8 p/n www.richtek.com 10 Width (mm) Max. 4.8 4.8 2.8 2.8 2.1 2.1 6 1.8 6 3 3.9 5 3.8 4.8 Height Inductance (mm) (μH) Max. L 1.2 1 1.4 2.2 1 2.2 1.2 2.2 1 2.2 1.2 2.2 4.5 1 1.8 2.2 2 2.2 1.5 2.2 1.7 3.3 3 3.3 1.8 3.3 1.8 3.3 RDC (mΩ) Max. 50 73 120 100 228 153 19 130 34 60 80 34 70 65 IDC (A) Supplier Max. 3.3 3 1 TDK 1 1 1 4.2 1 TAIYO 2.7 1.48 2.2 CoilCraft 2.26 Toko 1.55 1.95 Wurth DS9996-01 April 2011 RT9996 Thermal Considerations Layout Considerations For continuous operation, do not exceed absolute 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 : Follow the PCB layout guidelines for optimal performance of RT9996. PD(MAX) = (TJ(MAX) − TA) / θJA where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction to ambient thermal resistance. For recommended operating condition specifications of the RT9996, the maximum junction temperature is 125°C and TA is the ambient temperature. The junction to ambient thermal resistance, θJA, is layout dependent. For VQFN- ` Place the input capacitor as close as possible to the device pins (VIN and GND). ` LX node is with high frequency voltage swing and should be kept in a small area. ` Connect feedback network behind the output capacitors. ` Keep the switching area small. Place the feedback components near the RT9996. ` Connect all analog grounds to a common node and then connect the common node to the power ground behind the output capacitors. 32L 5x5 packages, the thermal resistance, θJA , is 36°C/ W on a standard JEDEC 51-7 four-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : PD(MAX) = (125°C − 25°C) / (36°C/W) = 2.778W for VQFN-32L 5x5 package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA . For the RT9996 package, the derating curve in Figure 3 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. Maximum Power Dissipation (W)1 3.0 Four-Layer PCB 2.7 2.4 2.1 1.8 1.5 1.2 0.9 0.6 0.3 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 3. Derating Curve for the RT9996 Package DS9996-01 April 2011 www.richtek.com 11 RT9996 Outline Dimension D2 D SEE DETAIL A L 1 E E2 e b 1 2 2 DETAIL A Pin #1 ID and Tie Bar Mark Options A A1 1 A3 Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.800 1.000 0.031 0.039 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 D 4.950 5.050 0.195 0.199 D2 3.400 3.750 0.134 0.148 E 4.950 5.050 0.195 0.199 E2 3.400 3.750 0.134 0.148 e L 0.500 0.350 0.020 0.450 0.014 0.018 V-Type 32L QFN 5x5 Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 5F, No. 95, Minchiuan Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)86672399 Fax: (8862)86672377 Email: [email protected] Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek. www.richtek.com 12 DS9996-01 April 2011