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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(R) mode, reducing the total current draw while in this mode to less than 30A. In LOWQ(R) mode, the output noise of the DC/DC converter is 53VRMS, significantly lower than other converters that use a PFM light load mode that can interfere with sensitive RF circuitry. The MIC2810 is a Cap 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(R) leadless package. Data sheets and support documentation can be found on Micrel's web site at: www.micrel.com.
DC/DC Converter * 2.7V to 5.5V input voltage range * Output current to 600mA in PWM mode * LOWQ(R) Mode: NO NOISE light load mode - 53VRMS Output noise in LOWQ(R) 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
Features
* 2MHz DC/DC converter and two LDOs * Integrated power-on reset (OR function for all outputs) - Adjustable delay time * LOWQ(R) mode - 30A Total IQ when in LOWQ(R) mode * Tiny 16-pin 3mm x 3mm MLF(R) package * Thermal shutdown protection * Current limit protection
Typical Application
1.2VOUT Efficiency
MIC2810-xxxYML
VIN 2.7V to 5.5V 4.7F
90
VOUT 2.2H 2.2F
VIN VIN1 VIN2 EN EN1 LOWQ EN2 BIAS PGND
0.1F
LDO SW
80
Memory/DSP
70 60
VIN=3V VIN=3.6V VIN=4.2V
LDO1 LDO2 POR CSET SGND
0.01F
50
Baseband
2.2F ceramic 2.2F ceramic
40 30 20
GND
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
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Micrel, Inc.
MIC2810
Ordering Information
Part number MIC2810-1.2/1.2/2.8YML MIC2810-1.2/1.8/2.6YML MIC2810-1.2/1.8/2.8YML MIC2810-1.2/1.8/3.0YML MIC2810-1.2/1.8/3.3YML MIC2810-1.2/2.7/3.3YML MIC2810-1.2/2.8/3.3YML
Notes: Other voltage options available. Please contact Micrel for details. DC/DC - Fixed Output Voltages. 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.
Manufacturing Part Number MIC2810-44MYML MIC2810-4GKYML MIC2810-4GMYML MIC2810-4GPYML MIC2810-4GSYML MIC2810-4LSYML MIC2810-4MSYML
Voltage* 1.2V/1.2V/2.8V 1.2V/1.8V/2.6V 1.2V/1.8V/2.8V 1.2V/1.8V/3.0V 1.2V/1.8V/3.3V 1.2V/2.7V/3.3V 1.2V/2.8V/3.3V
Junction Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Package 16-Pin 3x3 MLF(R) 16-Pin 3x3 MLF(R) 16-Pin 3x3 MLF(R) 16-Pin 3x3 MLF(R) 16-Pin 3x3 MLF(R) 16-Pin 3x3 MLF(R) 16-Pin 3x3 MLF(R)
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Pin Configuration
(R) 16-Pin 3mm x 3mm MLF (ML)
Pin Description
Pin Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Pin Name /LOWQ BIAS SGND PGND SW VIN VIN2 LDO2 LDO VIN1 LDO1 POR CSET EN1 EN EN2 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 0.1F 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
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Absolute Maximum Ratings(1)
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.)...................... 260C Storage Temperature (Ts) .........................-65C to +150C ESD Rating(4) .................................................................. 2kV
Operating Ratings(2)
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) ........................ -40C to +125C Junction Thermal Resistance MLF-16 (JA) ......................................................56C/W
Electrical Characteristics(5)
VIN = VIN1 = VIN2 = EN1 = EN2 = EN = /LOWQ = VOUT(6) + 1V; COUTDC/DC = 2.2F, CLDO1 = CLDO2 = 2.2F; IOUTDC/DC = 100mA; IOUTLDO1 = IOUTLDO2 = 100A; TJ = 25C, bold values indicate -40C < TJ < +125C; unless noted.
Parameter UVLO Threshold UVLO Hysteresis Ground Pin Current Conditions Rising input voltage during turn-on VFB = GND (not switching); LDO1 or LDO2 (EN = GND; EN1 or EN2 = GND) Ground Pin Current in Shutdown Ground Pin Current (LOWQ(R) mode) EN = EN1 = EN2 = 0V IDC/DC < ILDO1 < ILDO2 < 10mA (/LOWQ = GND) LDO1 or LDO2 (EN = GND; EN1 or EN2 = GND); IOUT < 10mA (/LOWQ = GND) 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 = 250A IPOR Flag Leakage Current, Flag OFF SET INPUT SET Pin Current Source VSET = 0V SET Pin Threshold Voltage POR = High Min 2.45 Typ 2.55 100 800 55 0.2 38 20 160 23 Max 2.65 1100 85 95 5 60 80 70 Units V mV A A A A A A A C C
0.2 1.0 0.1 0.1 240 83 1 1 500 350
V V A A s s
90
91 96 10 0.01 99 100 1 1.75
% % mV A A V
0.75
1.25 1.25
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Electrical Characteristics - DC/DC Converter
VIN = VOUTDC/DC + 1; EN = VIN; EN2 = EN1 = GND; IOUTDC/DC = 100mA ;L = 2.2H; COUTDC/DC = 2.2F; TJ = 25C, bold values indicate -40C to + 125C; unless noted.
Parameter 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 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 VFB = 0.9*VNOM -2 -3 0.2 0.1 100 0.5 0.6 2 1 +2 +3 % % %/V % % MHz A % % %/V %/V % dB mA VRMS Conditions Min Typ Max Units
1.8 0.75 -2 -3
2.2 1.6 +2 +3 0.3 0.6 1.5 220
LOWQ = Low (Light Load Mode) Output Voltage Accuracy Variation from nominal VOUT Variation from nominal VOUT; -40C to +125C Line Regulation VIN = VOUT + 1V to 5.5V; IOUT = 100A Load Regulation Ripple Rejection Current Limit Output Voltage Noise IOUT = 100A to 50mA f = up to 1kHz VOUT = 0V 10Hz to 100KHz
0.02 0.4 45 120 53
80
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Electrical Characteristics - LDO1/LDO2
VIN1 = VIN2 = VOUTLDO1 + 1.0V or VIN1 = VIN2 = VOUTLDO2 + 1.0V; EN = GND; EN1 = EN2 = VIN1 = VIN2; CLDO1 = CLDO2 = 2.2F; IOUTLDO1 = 100A; TJ = 25C, bold values indicate -40C< TJ < +125C; unless noted.
Parameter Conditions Min -2 -3 0.02 0.20 0.25 0.40 70 94 142 35 600 91 Typ Max +2 +3 0.3 0.6 1.5 Units % % %/V % % % mV mV mV dB mA VRMS % % %/V % mV mV dB mA LOWQ = High (Full Power Mode) Output Voltage Accuracy Variation from nominal VOUT Variation from nominal VOUT; -40C to +125C Line Regulation VIN = VOUT +1V to 5.5V Load Regulation IOUT = 100A to 150mA IOUT = 100A to 200mA IOUT = 100A to 300mA IOUT = 150mA IOUT = 200mA IOUT = 300mA f = up to 1kHz VOUT = 0V 10Hz to 100kHz
Dropout Voltage
300 850
Ripple Rejection Current Limit Output Voltage Noise
400
LOWQ = Low (Light Load Mode) Output Voltage Accuracy Variation from nominal VOUT Variation from nominal VOUT; -40C to +125C Line Regulation VIN = VOUT +1V to 5.5V Load Regulation Dropout Voltage Ripple Rejection Current Limit
Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating.
-3 -4 0.02 0.2 22 35 85
IOUT = 100A to 10mA IOUT = 10mA f = up to 1kHz VIN = 2.7V; VOUT = 0V
+3 +4 0.3 0.6 1.0 35 50 125
50
3. The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = (TJ(max) - TA) / JA. 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.
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Typical Characteristics DC/DC Normal Mode (/LOWQ = VIN)
1.2VOUT Efficiency
90 80 70 60 50 40 30 20 10 0 100 200 300 400 500 600 OUTPUT CURRENT (mA) VIN=3V VIN=3.6V VIN=4.2V 2.4 2.3 2.2 2.1 2.0 1.9 1.8 L = 2.2H COUT = 2.2F IOUT = 300mA /LowQ = VIN
Switching Frequency vs. Input Voltage
1.7 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT CURRENT (V)
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)
Switching Frequency vs. Temperature
Load Regulation
1.22 1.200
Line Regulation
1.8 1.6
Current Limit vs. Input Voltage
1.21
1.198
1.4 1.2 1.0 L = 2.2H COUT = 2.2F IOUT = 300mA /LowQ = VIN 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)
1.20 L = 2.2H COUT = 2.2F VIN = 3.6V /LowQ = VIN 100 200 300 400 500 600 OUTPUT CURRENT (mA)
1.196
1.19
1.194
1.18 0
1.192 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V)
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Typical Characteristics DC/DC LOWQ Mode (/LOWQ = GND)
80 70 60 50 40 30 VIN = 3.6V 20 VOUT = 1.2V COUT = 2.2F 10 IOUT = 5mA /LowQ = GND 0 0.01 0.1 1 10 100 FREQUENCY (kHz)
Power Supply Rejection Ratio
Load Regulation
1.24 1.23 1.22 1.21 1.20 1.19 1.18 1.17 1000 1.16 0 COUT = 2.2F VIN = 3.6V /LowQ = GND 10 20 30 40 50 60 70 80 OUTPUT CURRENT (mA)
1.15 1.20 1.25 1.30
Line Regulation
1.10 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V)
COUT = 2.2F VIN = 3.6V IOUT = 20mA /LowQ = GND
380 340 300 260 220 180 140 100 60
Current Limit vs. Input Voltage
10
Output Noise Spectral Density
1
0.1
/LowQ = GND 20 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V)
0.01 VIN = 4.2V VOUT = 1.2V COUT = 2.2F /LowQ = GND 0.001 0.01 0.1 1 10 100 1,000 10,000 FREQUENCY (kHz)
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MIC2810
Typical Characteristics LDO1/LDO2
80 70 60 50 40 30 20 10 0 0.01 0.1 1 10 100 FREQUENCY (kHz) 1000
Power Supply Rejection Ratio LDO1[LOWQ Mode]
VIN = 3.6V VOUT = 1.2V COUT = 2.2F IOUT = 25mA /LowQ = GND
70 60 50 40 30 20 10
Power Supply Rejection Ratio LDO1[Normal Mode]
VIN = 3.6V VOUT = 1.2V COUT = 2.2F IOUT = 100mA /LowQ = VIN
LDO1 Line Regulation
2.0
1.9
1.8 COUT = 2.2F VIN = 3.6V IOUT = 150mA /LowQ = VIN
1.7
0 0.01
0.1 1 10 100 FREQUENCY (kHz)
1000
1.6 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 INPUT VOLTAGE (V)
90 80 70 60 50 40 30 20 10
Power Supply Rejection Ratio LDO2[LOWQ Mode]
VIN = 3.6V VOUT = 2.8V COUT = 2.2F IOUT = 25mA /LowQ = GND
80 70 60 50 40 30 20 10
Power Supply Rejection Ratio LDO2[Normal Mode]
VIN = 3.6V VOUT = 2.8V COUT = 2.2F IOUT = 100mA /LowQ = VIN
LDO2 Load Regulation
2.85
2.80
2.75 COUT = 2.2F VIN = 3.6V /LowQ = VIN 50 100 150 200 250 300 OUTPUT CURRENT (mA)
0 0.01
0.1 1 10 100 FREQUENCY (kHz)
1000
0 0.01
0.1 1 10 100 FREQUENCY (kHz)
1000
2.70 0
80 75 70 65 60 55 0
LDO2 Ground Current vs. Output Current
80 70 60 50
LDO2 Ground Current vs. Temperature
140 120 100 80 60 40
LDO2 Dropout Voltage vs. Output Current
VIN = 3.6V VOUT = 2.8V /LowQ = VIN 50 100 150 200 250 300 OUTPUT CURRENT (mA)
40
30 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
VIN = 3.6V IOUT = 200mA /LowQ = VIN
20 0 0
VOUT = 2.8V /LowQ = VIN 50 100 150 200 250 300 OUTPUT CURRENT (mA)
110 100 90
LDO2 Dropout Voltage vs. Temperature
10
LDO2 Output Noise Spectral Density
1
0.1 80 70 VOUT = 2.8V IOUT = 200mA /LowQ = VIN 0.01 VIN = 4.2V VOUT = 2.8V COUT = 2.2F /LowQ = VIN 0.001 0.01 0.1 1 10 100 1,000 10,000 FREQUENCY (kHz)
60 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
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Functional Characteristics
LDO2[LOWQ Mode] Load Transient
LDO2[Normal Mode] Load Transient
VIN = 3.6V VOUT = 2.8V COUT = 2.2F /LowQ = VIN
Output Voltage AC Coupled (50mV/div)
45mA VIN = 3.6V VOUT = 2.8V COUT = 2.2F /LowQ = GND
Output Voltage AC Coupled (50mV/div)
200mA Output Current DC Coupled (100mA/div)
Output Current DC Coupled (20mA/div)
1mA
10mA
Time (100s/div)
Time (40s/div)
DC/DC[LOWQ Mode] Load Transient
DC/DC[LOWQ Mode] Start-Up Waveforms
Output Voltage AC Coupled (20mV/div)
50mA VIN = 3.6V VOUT = 1.2V COUT = 2.2F /LowQ = GND
Enable Voltage DC Coupled (2V/div)
Output Current DC Coupled (20mA/div)
1mA
Output Voltage DC Coupled (500mV/div)
VIN = 3.6V VOUT = 1.2V COUT = 2.2F /LowQ = GND IOUT = 20mA
Time (40s/div)
Time (20s/div)
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MIC2810
Functional Characteristics (cont.)
DC/DC PWM Waveforms
Output Voltage AC Coupled (20mV/div)
DC/DC Load Transient
VIN = 3.6V VOUT = 1.2V COUT = 2.2F
Switch Voltage Inductor Current DC Coupled DC Coupled (200mA/div) (2V/div)
Output Voltage AC Coupled (50mV/div)
L = 2.2H /LowQ = VIN IOUT = 300mA
300mA Output Current DC Coupled (200mA/div)
VIN = 3.6V VOUT = 1.2V COUT = 2.2F L = 2.2H /LowQ = VIN
10mA
Time (400ns/div)
Time (20s/div)
DC/DC Start-Up Waveforms
Enable Voltage DC Coupled (2V/div)
Output Voltage DC Coupled (500mV/div)
VIN = 3.6V VOUT = 1.2V COUT = 2.2F L = 2.2H /LowQ = VIN IOUT = 300mA Time (20s/div)
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Functional Diagram
MIC2810 Block Diagram
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MIC2810 LDO1 Regulated output voltage of LDO1. Power is provided by VIN1. Recommended output capacitance is 2.2F. LDO2 Regulated output voltage of LDO2. Power is provided by VIN2. Recommended output capacitance is 2.2F. 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 <1A). 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. /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 38A. 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. BIAS The BIAS pin supplies the power to the internal control and reference circuitry. The bias is powered from VIN through an internal 6 resistor. A small 0.1F capacitor is recommended for bypassing.
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 30A 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.
Pin Functional Description
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 4.7F 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. 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.
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Micrel, Inc. 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. 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 1.25A 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 (s) = CSET (pF)
MIC2810 Input Capacitor A minimum 1F ceramic, 4.7F 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 1F 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. Inductor Selection The MIC2810 is designed for use with a 2.2H 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 40C 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:
V VOUT 1 - OUT VIN IPK = IOUT + 2x f xL Peak Inductor Current Output/Load Current Input Voltage Output Voltage Switching Frequency of PWM Regulator Inductor Value
Component Selection
Output Capacitor LDO1 and LDO2 outputs require a 2.2F ceramic output capacitor for stability. The DC/DC switch mode regulator also requires a 2.2F ceramic output capacitor to be stable. All output capacitor values can be increased to improve transient response, but performance has been optimized for a 2.2F 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.
IPK: IOUT: VIN: VOUT: f: L:
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PCB Layout
EN J9 EN1 J10 R2
Vin
R3 R4
Vin
EN2 J11 /LowQ J12 JP1 R5 C5
16 15
EN2 EN
14
EN1
13
C4
R1
CSET
POR J8
1 /LowQ 2
BIAS
POR LDO1
12 11
Vin Vo
C3 C2
LD01 J4
3 SGND 4 PGND
VIN2 SW VIN
10 VIN1 9
LDO LDO2
LD0 J3
VO J6 GND J7
Vo
5 C7 L1 VIN J1
6
Vin
7
8 C6 LD02 J5
C1
GND J2
Layout Schematic
April 2007
15
M9999-041107-B
Micrel, Inc.
MIC2810
Top Layer
April 2007
16
M9999-041107-B
Micrel, Inc.
MIC2810
Bottom Layer
April 2007
17
M9999-041107-B
Micrel, Inc.
MIC2810
Package Information
16-Pin 3mm x 3mm MLF(R) (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. (c) 2006 Micrel, Incorporated.
April 2007
18
M9999-041107-B

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