MIC2810 Digital Power Management IC 2MHz, 600mA DC/DC w/Dual 300mA/300mA Low VIN LDOs General Description The MIC2810 is a high performance power management IC, integrating a 2MHz DC/DC switcher with two 300mA LDOs. The MIC2810 features a LOWQ® mode, reducing the total current draw while in this mode to less than 30µA. In LOWQ® mode, the output noise of the DC/DC converter is 53µVRMS, significantly lower than other converters that use a PFM light load mode that can interfere with sensitive RF circuitry. The MIC2810 is a µCap design, operating with very small ceramic output capacitors and inductors for stability, therefore, reducing required board space and component cost. It is available with fixed output voltages in a 16-pin 3mm x 3mm MLF® leadless package. Data sheets and support documentation can be found on Micrel’s web site at: www.micrel.com. Features • 2MHz DC/DC converter and two LDOs • Integrated power-on reset (OR function for all outputs) – Adjustable delay time • LOWQ® mode – 30µA Total IQ when in LOWQ® mode • Tiny 16-pin 3mm x 3mm MLF® package • Thermal shutdown protection • Current limit protection DC/DC Converter • 2.7V to 5.5V input voltage range • Output current to 600mA in PWM mode • LOWQ® Mode: NO NOISE light load mode – 53µVRMS Output noise in LOWQ® mode • 2MHz PWM operation in normal mode LDOs • LDO1 – 1.65V to 5.5V input voltage range – 300mA Output current – Output voltage down to 0.8V • LDO2 – 2.7V to 5.5V input voltage range – 300mA Output current – Output voltage down to 0.8V Applications • • • • • Mobile phones PDAs GPS receivers Digital still cameras Portable media players Typical Application 1.2VOUT Efficiency 90 MIC2810-xxxYML VIN 2.7V to 5.5V 4.7µF VIN VIN1 VIN2 EN EN1 LOWQ EN2 BIAS PGND 0.1µF LDO SW VOUT 2.2µH 80 Memory/DSP 70 2.2µF 60 LDO1 LDO2 POR CSET SGND 50 Baseband 2.2µF ceramic VIN=4.2V 40 2.2µF ceramic 30 20 0.01µF GND VIN=3V VIN=3.6V GND 10 0 100 200 300 400 500 600 OUTPUT CURRENT (mA) LOWQ is a registered trademark of Micrel, Inc. MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com February 2008 M9999-022008-C Micrel, Inc. MIC2810 Ordering Information Part Number Marking Code Voltage* Junction Temperature Range Package MIC2810-44MYML YD44M 1.2V/1.2V/2.8V –40°C to +125°C 16-Pin 3x3 MLF® Pb-Free –40°C to +125°C 16-Pin 3x3 MLF ® Pb-Free ® Pb-Free MIC2810-4GKYML YD4GK 1.2V/1.8V/2.6V Lead Finish MIC2810-4GMYML YD4GM 1.2V/1.8V/2.8V –40°C to +125°C 16-Pin 3x3 MLF MIC2810-4GPYML YD4GP 1.2V/1.8V/3.0V –40°C to +125°C 16-Pin 3x3 MLF® Pb-Free –40°C to +125°C 16-Pin 3x3 MLF ® Pb-Free ® Pb-Free MIC2810-4GSYML YD4GS 1.2V/1.8V/3.3V MIC2810-4LSYML YD4LS 1.2V/2.7V/3.3V –40°C to +125°C 16-Pin 3x3 MLF MIC2810-4MSYML YD4MS 1.2V/2.8V/3.3V –40°C to +125°C 16-Pin 3x3 MLF® Pb-Free –40°C to +125°C 16-Pin 3x3 MLF ® Pb-Free 16-Pin 3x3 MLF ® Pb-Free MIC2810-CGJYML MIC2810-FGSYML YDCGJ YDFGS 1.2V/1.8V/2.5V 1.5V/1.8V/3.3V –40°C to +125°C Notes: MLF® is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. Other voltage options available. Please contact Micrel for details. DC/DC –Output Voltage Range of 1.0V to 2.0V. LDO1 – Output Voltage Range of 0.8V to 3.6V. LDO2 – Output Voltage Range of 0.8V to 3.6V. * Refers to nominal output voltage of DC/DC, LDO1, and LDO2 respectively. February 2008 2 M9999-022008-C Micrel, Inc. MIC2810 Pin Configuration ® 16-Pin 3mm x 3mm MLF (ML) Pin Description Pin Number Pin Name 1 /LOWQ 2 BIAS 3 4 5 SGND PGND SW 6 VIN 7 8 9 10 11 VIN2 LDO2 LDO VIN1 LDO1 12 POR 13 CSET 14 EN1 15 EN 16 EN2 February 2008 Pin Function LOWQ Mode. Active Low Input. Logic High = Full Power (Normal) Mode; Logic Low = LOWQ Mode; Do not leave floating. Internal circuit bias supply. It must be de-coupled to signal ground with a 0.1µF capacitor and should not be loaded. Signal ground. Power ground. Switch: Internal power MOSFET output switches. Supply Input – DC/DC and other circuitry shared with LDO1 and LDO2. Must be connected to PIN 7. Supply Input – LDO2. Must be connected to PIN 6. Output of LDO2 LDO Output: Connect to VOUT of the DC/DC for LOWQ mode operation. Supply Input – LDO1. Output of LDO1 Power-On Reset Output: Open-drain output. Active low indicates an output undervoltage condition on either one of the three regulated outputs. Delay Set Input: Connect external capacitor to GND to set the internal delay for the POR output. When left open, there is minimum delay. This pin cannot be grounded. Enable Input (LDO 1). Active High Input. Logic High = On; Logic Low = Off; Do not leave floating Enable Input (DC/DC). Active High Input. Logic High = On; Logic Low = Off; Do not leave floating. Enable Input (LDO 2). Active High Input. Logic High = On; Logic Low = Off; Do not leave floating 3 M9999-022008-C Micrel, Inc. MIC2810 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VIN, VIN1, VIN2)............................... 0V to 6V Enable Input Voltage (VEN, VEN1, VEN2)................... 0V to VIN Power Dissipation .................................. Internally Limited(3) Lead Temperature (soldering, 10 sec.)...................... 260°C Storage Temperature (Ts) .........................–65°C to +150°C ESD Rating(4) .................................................................. 2kV Supply Voltage (VIN, VIN2)................................. 2.7V to 5.5V Supply Voltage (VIN1)...................................... 1.65V to 5.5V Enable Input Voltage (VEN, VEN1, VEN2)................... 0V to VIN Junction Temperature (TJ) ........................ –40°C to +125°C Junction Thermal Resistance MLF-16 (θJA) ......................................................56°C/W Electrical Characteristics(5) VIN = VIN1 = VIN2 = EN1 = EN2 = EN = /LOWQ = VOUT(6) + 1V; COUTDC/DC = 2.2µF, CLDO1 = CLDO2 = 2.2µF; IOUTDC/DC = 100mA; IOUTLDO1 = IOUTLDO2 = 100µA; TJ = 25°C, bold values indicate –40°C < TJ < +125°C; unless noted. Parameter UVLO Threshold UVLO Hysteresis Ground Pin Current Ground Pin Current in Shutdown Ground Pin Current (LOWQ® mode) Conditions Rising input voltage during turn-on VFB = GND (not switching); Typ 2.55 100 800 LDO1 or LDO2 (EN = GND; EN1 or EN2 = GND) 55 EN = EN1 = EN2 = 0V 0.2 IDC/DC < ILDO1 < ILDO2 < 10mA (/LOWQ = GND) 38 LDO1 or LDO2 (EN = GND; EN1 or EN2 = GND); IOUT < 10mA (/LOWQ = GND) 20 Over-temperature Shutdown Over-temperature Shutdown Hysteresis Enable Inputs (EN; EN1; EN2; /LOWQ ) Enable Input Voltage Logic Low Logic High Enable Input Current VIL < 0.2V VIH > 1.0V Turn-on Time Turn-on Time (LDO1 and LDO2) Turn-on Time (DC/DC) (/LOWQ = VIN; ILOAD = 300mA); (/LOWQ = GND; ILOAD = 10mA) POR Output VTH Low Threshold, % of nominal (VDC/DC or VLDO1 or VLDO2) (Flag ON) High Threshold, % of nominal (VDC/DC AND VLDO1 AND VLDO2) (Flag OFF) VOL POR Output Logic Low Voltage; IL = 250µA IPOR Flag Leakage Current, Flag OFF SET INPUT SET Pin Current Source VSET = 0V SET Pin Threshold Voltage POR = High February 2008 Min 2.45 4 Max 2.65 1100 Units V mV µA 85 95 5 µA µA µA 60 80 70 µA µA µA °C °C 160 23 0.2 0.1 0.1 1 1 V V µA µA 240 500 µs 83 350 µs 1.0 90 0.75 91 % 96 99 % 10 0.01 100 1 mV µA 1.25 1.25 1.75 µA V M9999-022008-C Micrel, Inc. MIC2810 Electrical Characteristics - DC/DC Converter VIN = VOUTDC/DC + 1; EN = VIN; EN2 = EN1 = GND; IOUTDC/DC = 100mA ;L = 2.2µH; COUTDC/DC = 2.2µF; TJ = 25°C, bold values indicate –40°C to + 125°C; unless noted. Parameter Conditions Min Typ Max Units LOWQ = High (Full Power Mode) Fixed Output Voltages Output Voltage Line Regulation Output Voltage Load Regulation Maximum Duty Cycle PWM Switch ON-Resistance Oscillator Frequency Current Limit in PWM Mode Nominal VOUT tolerance –2 –3 VOUT > 2.4V; VIN = VOUT + 300mV to 5.5V, ILOAD= 100mA VOUT < 2.4V; VIN = 2.7V to 5.5V, ILOAD= 100mA 20mA < ILOAD < 600mA VFB ≤ 0.4V ISW = 150mA VFB = 0.7VFB_NOM PMOS ISW = -150mA VFB = 1.1VFB_NOM NMOS LOWQ = Low (Light Load Mode) Output Voltage Accuracy Variation from nominal VOUT Variation from nominal VOUT; –40°C to +125°C Line Regulation VIN = VOUT + 1V to 5.5V; IOUT = 100µA Load Regulation Ripple Rejection Current Limit IOUT = 100µA to 50mA f = up to 1kHz VOUT = 0V Output Voltage Noise 10Hz to 100KHz February 2008 %/V 0.1 % % Ω Ω MHz A 0.5 0.6 2 1 –2 –3 0.02 80 0.4 45 120 53 5 % % 0.2 100 1.8 0.75 VFB = 0.9*VNOM +2 +3 2.2 1.6 +2 +3 0.3 0.6 1.5 220 % % %/V %/V % dB mA µVRMS M9999-022008-C Micrel, Inc. MIC2810 Electrical Characteristics – LDO1/LDO2 VIN1 = VIN2 = VOUTLDO1 + 1.0V or VIN1 = VIN2 = VOUTLDO2 + 1.0V; EN = GND; EN1 = EN2 = VIN1 = VIN2; CLDO1 = CLDO2 = 2.2µF; IOUTLDO1 = 100µA; TJ = 25°C, bold values indicate –40°C< TJ < +125°C; unless noted. Parameter Conditions Min LOWQ = High (Full Power Mode) Output Voltage Accuracy Variation from nominal VOUT Variation from nominal VOUT; –40°C to +125°C Line Regulation VIN = VOUT +1V to 5.5V –2 –3 Load Regulation Dropout Voltage Ripple Rejection Current Limit Output Voltage Noise IOUT = 100µA to 150mA IOUT = 100µA to 200mA IOUT = 100µA to 300mA IOUT = 150mA IOUT = 200mA IOUT = 300mA f = up to 1kHz VOUT = 0V 10Hz to 100kHz Load Regulation Dropout Voltage IOUT = 100µA to 10mA IOUT = 10mA Ripple Rejection Current Limit f = up to 1kHz VIN = 2.7V; VOUT = 0V 0.02 400 LOWQ = Low (Light Load Mode) Output Voltage Accuracy Variation from nominal VOUT Variation from nominal VOUT; –40°C to +125°C Line Regulation VIN = VOUT +1V to 5.5V Typ 0.20 0.25 0.40 70 94 142 35 600 91 –3 –4 0.02 0.2 22 50 35 85 Max Units +2 +3 0.3 0.6 % % %/V 1.5 300 850 +3 +4 0.3 0.6 1.0 35 50 125 % % % mV mV mV dB mA µVRMS % % %/V % mV mV dB mA Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = (TJ(max) – TA) / θJA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 4. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. 5. Specification for packaged product only. February 2008 6 M9999-022008-C Micrel, Inc. MIC2810 Typical Characteristics ― DC/DC Normal Mode (/LOWQ = VIN) 1.2VOUT Efficiency 90 2.4 80 2.3 70 60 50 VIN=3V 2.2 VIN=3.6V 2.1 VIN=4.2V 2.0 40 1.9 30 1.8 20 10 0 Switching Frequency vs. Input Voltage 100 200 300 400 500 600 OUTPUT CURRENT (mA) L = 2.2µH COUT = 2.2µF IOUT = 300mA /LowQ = VIN 1.7 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT CURRENT (V) Load Regulation Switching Frequency vs. Temperature 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 VIN = 3.6V 1.5 IOUT = 400mA 1.4 /LowQ = VIN 1.3 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) Line Regulation 1.22 1.200 1.21 1.198 1.20 1.196 1.8 Current Limit vs. Input Voltage 1.6 L = 2.2µH COUT = 2.2µF VIN = 3.6V /LowQ = VIN 1.19 1.18 0 100 200 300 400 500 600 OUTPUT CURRENT (mA) February 2008 1.194 1.4 1.2 1.0 L = 2.2µH COUT = 2.2µF IOUT = 300mA /LowQ = VIN 1.192 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) 7 0.8 0.6 /LowQ = VIN 0.4 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) M9999-022008-C Micrel, Inc. MIC2810 Typical Characteristics ― DC/DC LOWQ Mode (/LOWQ = GND) 80 Power Supply Rejection Ratio Load Regulation 1.24 70 1.23 60 1.22 50 1.21 40 1.20 30 1.19 VIN = 3.6V 20 VOUT = 1.2V COUT = 2.2µF 10 IOUT = 5mA /LowQ = GND 0 0.01 0.1 1 10 100 FREQUENCY (kHz) 380 1.18 1.17 1000 Current Limit vs. Input Voltage 1.16 0 10 Line Regulation 1.30 1.25 1.20 COUT = 2.2µF VIN = 3.6V /LowQ = GND 10 20 30 40 50 60 70 80 OUTPUT CURRENT (mA) 1.15 COUT = 2.2µF VIN = 3.6V IOUT = 20mA /LowQ = GND 1.10 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) Output Noise Spectral Density 340 300 1 260 220 180 0.1 140 100 60 /LowQ = GND 20 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) February 2008 0.01 VIN = 4.2V VOUT = 1.2V COUT = 2.2µF /LowQ = GND 0.001 0.01 0.1 1 10 100 1,000 10,000 FREQUENCY (kHz) 8 M9999-022008-C Micrel, Inc. MIC2810 Typical Characteristics ― LDO1/LDO2 Power Supply Rejection Ratio LDO1[LOWQ Mode] 80 VIN = 3.6V VOUT = 1.2V COUT = 2.2µF IOUT = 25mA /LowQ = GND 70 60 50 70 60 50 20 20 2.0 1.9 1.7 10 10 0.1 1 10 100 FREQUENCY (kHz) 1000 Power Supply Rejection Ratio LDO2[LOWQ Mode] 90 VIN = 3.6V VOUT = 2.8V COUT = 2.2µF IOUT = 25mA /LowQ = GND 80 70 60 50 0 0.01 0.1 1 10 100 FREQUENCY (kHz) 1000 Power Supply Rejection Ratio LDO2[Normal Mode] 80 70 60 50 VIN = 3.6V VOUT = 2.8V COUT = 2.2µF IOUT = 100mA /LowQ = VIN COUT = 2.2µF VIN = 3.6V IOUT = 150mA /LowQ = VIN 1.6 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V) LDO2 Load Regulation 2.85 2.80 40 40 30 30 20 20 10 10 80 LDO1 Line Regulation 1.8 30 30 0 0.01 VIN = 3.6V VOUT = 1.2V COUT = 2.2µF IOUT = 100mA /LowQ = VIN 40 40 0 0.01 Power Supply Rejection Ratio LDO1[Normal Mode] 0.1 1 10 100 FREQUENCY (kHz) 1000 LDO2 Ground Current vs. Output Current 0 0.01 80 2.75 0.1 1 10 100 FREQUENCY (kHz) 1000 LDO2 Ground Current vs. Temperature 2.70 0 140 COUT = 2.2µF VIN = 3.6V /LowQ = VIN 50 100 150 200 250 300 OUTPUT CURRENT (mA) LDO2 Dropout Voltage vs. Output Current 120 75 70 70 60 80 65 50 60 100 40 60 55 0 110 VIN = 3.6V VOUT = 2.8V /LowQ = VIN 50 100 150 200 250 300 OUTPUT CURRENT (mA) LDO2 Dropout Voltage vs. Temperature 100 VIN = 3.6V IOUT = 200mA /LowQ = VIN 40 30 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) 10 20 0 0 VOUT = 2.8V /LowQ = VIN 50 100 150 200 250 300 OUTPUT CURRENT (mA) LDO2 Output Noise Spectral Density 1 90 0.1 80 70 VOUT = 2.8V IOUT = 200mA /LowQ = VIN 60 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C) February 2008 0.01 VIN = 4.2V VOUT = 2.8V COUT = 2.2µF /LowQ = VIN 0.001 0.01 0.1 1 10 100 1,000 10,000 FREQUENCY (kHz) 9 M9999-022008-C Micrel, Inc. MIC2810 Functional Characteristics LDO2[LOWQ Mode] Load Transient VIN = 3.6V VOUT = 2.8V COUT = 2.2µF /LowQ = VIN Output Voltage AC Coupled (50mV/div) Output Voltage AC Coupled (50mV/div) LDO2[Normal Mode] Load Transient 200mA 1mA Output Current DC Coupled (100mA/div) VIN = 3.6V VOUT = 2.8V COUT = 2.2µF /LowQ = GND Time (40µs/div) DC/DC[LOWQ Mode] Load Transient DC/DC[LOWQ Mode] Start-Up Waveforms Enable Voltage DC Coupled (2V/div) VIN = 3.6V VOUT = 1.2V COUT = 2.2µF /LowQ = GND 1mA VIN = 3.6V VOUT = 1.2V COUT = 2.2µF /LowQ = GND IOUT = 20mA Output Voltage DC Coupled (500mV/div) Output Current DC Coupled (20mA/div) 50mA Time (20µs/div) Time (40µs/div) February 2008 10mA Time (100µs/div) Output Voltage AC Coupled (20mV/div) Output Current DC Coupled (20mA/div) 45mA 10 M9999-022008-C Micrel, Inc. MIC2810 Functional Characteristics (cont.) L = 2.2µH /LowQ = VIN IOUT = 300mA Output Voltage AC Coupled (50mV/div) VIN = 3.6V VOUT = 1.2V COUT = 2.2µF DC/DC Load Transient Switch Voltage Inductor Current DC Coupled DC Coupled (200mA/div) (2V/div) Output Voltage AC Coupled (20mV/div) DC/DC PWM Waveforms Output Current DC Coupled (200mA/div) 300mA VIN = 3.6V VOUT = 1.2V COUT = 2.2µF L = 2.2µH /LowQ = VIN 10mA Time (20µs/div) Time (400ns/div) Enable Voltage DC Coupled (2V/div) DC/DC Start-Up Waveforms Output Voltage DC Coupled (500mV/div) VIN = 3.6V VOUT = 1.2V COUT = 2.2µF L = 2.2µH /LowQ = VIN IOUT = 300mA Time (20µs/div) February 2008 11 M9999-022008-C Micrel, Inc. MIC2810 Functional Diagram MIC2810 Block Diagram February 2008 12 M9999-022008-C Micrel, Inc. MIC2810 LDO1 Regulated output voltage of LDO1. Power is provided by VIN1. Recommended output capacitance is 2.2µF. Device Functional Description The MIC2810 is a power management IC with a single integrated step-down regulator and two low dropout regulators. LDO1 and LDO2 are 300mA low dropout regulators supplied from the input voltage pins. The step-down regulator is a 600mA PWM power supply. All three regulators utilize a /LOWQ light load mode to maximize battery efficiency under light load conditions. This is achieved with a /LOWQ control pin that when pulled low shuts down all the biasing and drive current for the PWM regulator, along with reducing the current limit of the two independent LDOs. When the /LOWQ pin is pulled low, the MIC2810 draws only 30µA of operating current. This mode allows the output to be regulated through the LDO output which is capable of providing 60mA of output current. This method has the advantage of producing a clean, low current, ultra-low noise output in /LOWQ mode. During /LOWQ mode, the SW node becomes high impedance, blocking current flow. Other methods of reducing quiescent current, such as pulse frequency modulation (PFM) or bursting techniques create large amplitude and low frequency ripple voltages that can be detrimental to system operation. When more than 60mA is required, the /LOWQ pin can be forced high, causing the MIC2810 to enter PWM mode. In this case, the LDO output makes a "hand-off" to the PWM regulator with virtually no variation in output voltage. The LDO output then turns off allowing up to 600mA of current to be efficiently supplied through the PWM output to the load. LDO2 Regulated output voltage of LDO2. Power is provided by VIN2. Recommended output capacitance is 2.2µF. EN/EN1/EN2 All enable inputs are active high, requiring 1.0V for guaranteed operation. EN provides logic control for the DC/DC regulator. EN2 provides logic control for LDO2, and EN1 provides logic control for LDO1. The enable inputs are CMOS logic and cannot be left floating. The enable pins provide logic level control of the specified outputs. When all enable pins are in the off state, supply current of the device is greatly reduced (typically <1µA). When the DC/DC regulator is in the off state, the output drive is placed in a "tri-stated" condition, where both the high side P-channel MOSFET and the low-side N-channel are in an “off” or non-conducting state. Do not drive any of the enable pins above the supply voltage. Power-On Reset (POR) The power-on reset output is an open-drain N-Channel device, requiring a pull-up resistor to either the input voltage or output voltage for proper voltage levels. The POR output has a delay time that is programmable with a capacitor from the CSET pin to ground. The delay time can be programmed to be as long as 1 second. Pin Functional Description /LOWQ The /LOWQ pin provides a logic level control between the internal PWM switching regulator mode, and the low noise linear regulator mode. With /LOWQ pulled low (≤0.2V), quiescent current of the device is greatly reduced by switching to a low noise linear regulator mode that has a typical supply current of 38µA. In linear (LDO) mode the output can deliver 60mA of current to the output. By placing /LOWQ high (≥1V), the device transitions into a constant frequency PWM step-down regulator mode. This allows the device the ability to efficiently deliver up to 600mA of output current at the same output voltage. /LOWQ mode also limits the output load of both LDO1 and LDO2 to <50mA. VIN/VIN1/VIN2 Three input voltage pins provide power to the switch mode regulator, LDO1, and LDO2. VIN provides power to the control circuitry of the DC/DC converter and voltage reference circuitry shared by all the regulators in the MIC2810. LDO1’s input voltage (VIN1) can go down to 1.65V but LDO2 and the DC/DC converter input voltages are limited to 2.7V minimum. For the switch mode regulator VIN provides power to the MOSFET along with current limiting sense circuitry. Due to the high switching speeds, a 4.7µF capacitor is recommended close to VIN and the power ground (PGND) pin for bypassing. Please refer to the PCB layout section for an example of an appropriate circuit layout. BIAS The BIAS pin supplies the power to the internal control and reference circuitry. The bias is powered from VIN through an internal 6Ω resistor. A small 0.1µF capacitor is recommended for bypassing. LDO The LDO pin is the output of the linear regulator and should be connected to the output of the step-down PWM regulator. In /LOWQ mode (/LOWQ <0.2V), the LDO provides the output voltage of the DC/DC regulator. February 2008 13 M9999-022008-C Micrel, Inc. MIC2810 Input Capacitor A minimum 1µF ceramic, 4.7µF recommended, should be placed as close as possible to the VIN pin for optimal bypassing. X5R or X7R dielectrics are recommended for the input capacitor. Y5V dielectrics lose most of their capacitance over temperature and are therefore, not recommended. A minimum 1µF is recommended close to the VIN and PGND pins for high frequency filtering. Smaller case size capacitors are recommended due to their lower ESR and ESL. Please refer to the PCB layout section for an example of an appropriate circuit layout. SW The switch (SW) pin connects directly to the inductor and provides the switching current necessary to operate in PWM mode. Due to the high speed switching on this pin, the switch node should be routed away from sensitive nodes. PGND Power ground (PGND) is the ground path for the high current PWM mode. The current loop for the power ground should be as small as possible. Inductor Selection The MIC2810 is designed for use with a 2.2µH inductor. Proper selection should ensure the inductor can handle the maximum average and peak currents required by the load. Maximum current ratings of the inductor are generally given in two methods; permissible DC current and saturation current. Permissible DC current can be rated either for a 40°C temperature rise or a 10% to 20% loss in inductance. Ensure that the inductor selected can handle the maximum operating current. When saturation current is specified, make sure that there is enough margin that the peak current will not saturate the inductor. Peak inductor current can be calculated as follows: SGND Signal ground (SGND) is the ground path for the biasing and control circuitry. The current loop for the signal ground should be as small as possible. CSET The CSET pin is a current source output that charges a capacitor that sets the delay time for the power-on reset output from low to high. The delay for POR high to low (detecting an undervoltage on any of the outputs) is always minimal. The current source of 1.25µA charges a capacitor up from 0V. When the capacitor reaches 1.25V, the output of the POR is allowed to go high. The delay time in microseconds is equal to the Cset in picofarads. POR Delay (µs) = CSET (pF) Component Selection IPK: IOUT: VIN: VOUT: f: L: Output Capacitor LDO1 and LDO2 outputs require a 2.2µF ceramic output capacitor for stability. The DC/DC switch mode regulator also requires a 2.2µF ceramic output capacitor to be stable. All output capacitor values can be increased to improve transient response, but performance has been optimized for a 2.2µF ceramic on the LDOs and the DC/DC regulator. X7R/X5R dielectric-type ceramic capacitors are recommended because of their temperature performance. X5R/X7R-type capacitors change capacitance by 15% over their operating temperature range and are the most stable type of ceramic capacitors. Z5U and Y5V dielectric capacitors change value by as much as 50% to 60% respectively over their operating temperature ranges. February 2008 14 ⎛ ⎞ V VOUT ⎜⎜1 − OUT ⎟⎟ VIN ⎠ ⎝ IPK = IOUT + 2× f ×L Peak Inductor Current Output/Load Current Input Voltage Output Voltage Switching Frequency of PWM Regulator Inductor Value M9999-022008-C Micrel, Inc. MIC2810 PCB Layout R3 Vin EN1 J10 R2 EN J9 R4 13 1 /LowQ 2 JP1 C5 POR LDO1 BIAS 3 SGND 5 C7 GND J7 L1 VIN J1 LDO2 VIN2 VIN 6 7 Vin POR J8 C3 LD01 J4 11 LDO SW VO J6 12 10 VIN1 9 4 PGND Vo R1 C4 CSET EN2 /LowQ J12 14 EN 16 15 EN1 EN2 J11 R5 Vin Vin Vo C2 LD0 J3 8 C6 C1 LD02 J5 GND J2 Layout Schematic February 2008 15 M9999-022008-C Micrel, Inc. MIC2810 Top Layer February 2008 16 M9999-022008-C Micrel, Inc. MIC2810 Bottom Layer February 2008 17 M9999-022008-C Micrel, Inc. MIC2810 Package Information 16-Pin 3mm x 3mm MLF® (ML) MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2006 Micrel, Incorporated. February 2008 18 M9999-022008-C