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MIC2800
Digital Power Management IC 2MHz, 600mA DC/DC w/Dual 300mA/300mA Low VIN LDOs
General Description
The MIC2800 is a high performance power management IC, giving three output voltages with maximum efficiency. Integrating a 2MHz DC/DC converter with an LDO post regulator, the MIC2800 gives two high efficiency outputs with a second, 300mA LDO for maximum flexibility. The MIC2800 features a LOWQTM mode, reducing the total current draw while in this mode to less than 30A. In LOWQTM mode, the output noise of the DC to DC converter is 75VRMS, significantly lower than other converters which use a PFM light load mode that can interfere with sensitive RF circuitry. The DC to DC converter uses small values of L and C to reduce board space but still retains efficiencies over 90% at load currents up to 600mA. The MIC2800 is a Cap design, operating with very small ceramic output capacitors and inductors for stability, reducing required board space and component cost and it is available in fixed output voltages in the 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.
* Integrated power-on reset (OR function for all outputs) - Adjustable delay time * LOWQTM mode - 30A Total IQ when in LOWQTM mode * Tiny 16-pin 3mm x 3mm MLF(R) package DC to DC Converter * Output current to 600mA in PWM mode * LOWQTM Mode: NO NOISE Light load mode - 75VRMS output noise in LOWQTM mode * 2MHz PWM operation in normal mode * >90% efficiency LDOs * LDO1 input voltage directly connected to DC/DC converter output voltage for maximum efficiency - Ideal for 1.8V to 1.5V conversion - 300mA output current from 1.8V input - Output voltage down to 0.8V * LDO2 - 300mA output current capable * Thermal Shutdown Protection * Current Limit Protection
Applications
* * * * * Mobile phones PDAs GPS receivers Digital still cameras Portable media players
Features
* 2.7V to 5.5V input voltage range * 2MHz DC/DC converter and two stand-alone LDOs - LDO1: Low input voltage is powered directly from DC/DC converter for highest efficiency
Typical Application
DC/DC 1.8VOUT Efficiency
MIC2800-xxxYML
VIN 2.7V to 5.5V 4.7F/ 6.3V
VIN VIN EN1 LOWQ EN2 CBYP CBIAS PGND
CBIAS 0.1F
LDO SW FB LDO1 LDO2 POR CSET SGND
CSET 0.01F
VOUT 2.2H 2.2F ceramic
Memory/DSP
Baseband
COUT2 2.2F ceramic COUT1 2.2F ceramic
CBYP 0.01F
100 95 3.6V 3V 90 85 4.2V 80 75 70 65 60 L = 2.2H COUT = 2.2F 55 /LowQ = VIN 50 0 100 200 300 400 500 600 OUTPUT CURRENT (mA)
GND
GND
LOWQ is a 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
June 2006
M9999-061406 (408) 955-1690
Micrel, Inc.
MIC2800
Ordering Information
Part number MIC2800-1.8/1.2/2.8YML MIC2800-1.87/1.2/2.8YML MIC2800-1.8/1.5/2.8YML MIC2800-Adj/1.2/3.3YML
Notes: Other voltage options available. Please contact Micrel for details. DC/DC - Fixed Output Voltages (Range of 1.0V to 2.0V). Adjustable output voltage is available upon request. LDO1 - Output Voltage Range of 0.8V to VDC/DC - VDO. LDO2 - Output Voltage Range of 0.8V to 3.6V.
Manufacturing Part Number MIC2800-G4MYML MIC2800-D24MYML MIC2800-GFMYML MIC2800-A4SYML
Voltage 1.8V/1.2V/2.8V 1.87V/1.2V/2.8V 1.8V/1.5V/2.8V Adj/1.2V/3.3V
Junction Temperature Range -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)
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MIC2800
Pin Configuration
(R) 3mm x 3mm MLF (ML)
Fixed DC/DC Converter Output Voltage
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 VIN LDO2 FB LDO LDO1 POR CSET CBYP EN1 EN2 Pin Function LOWQ Mode. Active Low Input. Logic High = Full Power 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 (Output): Internal power MOSFET output switches. Supply Input - DC/DC. Must be tied to PIN7 externally. Supply Input - LDO2. Must be tied to PIN6 externally. Output of regulator 2 Feedback. Input to the error amplifier for DC to DC converter. adjust version, co For fixed output voltages connect to VOUT and an internal resistor network sets the output voltage LDO Output: Connect to VOUT of the DC/DC for LOWQ mode operation. Output of regulator 1 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. Reference Bypass: Connect external 0.1F to GND to reduce output noise. May be left open. Enable Input (DC/DC and LDO1). 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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MIC2800
Absolute Maximum Ratings(1)
Supply Voltage (VIN) ............................................. 0V to +6V Enable Input Voltage (VEN)................................... 0V to +6V Power Dissipation, Internally Limited(3) Lead Temperature (soldering, 10 sec.)...................... 260C Storage Temperature (Ts) .........................-65C to +150C EDS Rating(4) .................................................................. 2kV
Operating Ratings(2)
Supply voltage (VIN) ..................................... +2.7V to +5.5V Enable Input Voltage (VEN)..................................... 0V to VIN Junction Temperature (TJ) ........................ -40C to +125C Junction Thermal Resistance MLF-16 (JA) ......................................................45C/W
Electrical Characteristics(5)
VIN = EN1 = EN2 = LOWQ = VOUT(6) + 1V; COUTDC/DC = 2.2F, COUT1 = COUT2 = 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); LDO2 Only (EN1 = LOW) Ground Pin Current in Shutdown Ground Pin Current (LOWQ mode) All EN = 0V IDC/DC < ILDO1 < ILDO2 < 10mA Min 2.45 Typ 2.55 100 800 55 0.2 30 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
DC/DC and LDO1 OFF; ILDO2 < 10mA Over-temperature Shutdown Over-temperature Shutdown Hysteresis Enable Inputs (EN1; EN2; /LOWQ ) Enable Input Voltage Logic Low Logic High Enable Input Current VIL < 0.2V VIH > 1.0V Turn-on Time (See Timing Diagram) Turn-on Time EN2=VIN (LDO1 and LDO2) EN1=VIN Turn-on Time (DC/DC) EN2=VIN; ILOAD = 300mA; CBYP = 0.1F 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
0.2 1.0 0.1 0.1 240 120 83 90 91 96 10 0.01 0.75 1.25 1.25 99 100 1 1.75 1 1 500 350 350
V V A A s s s % % mV A A V
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MIC2800
Electrical Characteristics - DC/DC Converter
VIN = VOUTDC/DC + 1; EN1 = VIN; EN2 = 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 Current Limit in PWM Mode FB pin input current (ADJ only) Output Voltage Line Regulation Output Voltage Load Regulation Maximum Duty Cycle PWM Switch ON-Resistance Oscillator Frequency Output Voltage Noise COUT = 2.2F; CBYP = 0.1F; 10Hz to 100KHz -2.0 -3.0 40 0.02 0.2 55 45 120 0.3 0.6 1.5 LOWQ = Low (Light Load Mode) Output Voltage Accuracy Variation from nominal VOUT Variation from nominal VOUT; -40C to +125C Output Voltage Temp. Coefficient Line Regulation VIN = VOUT + 1V to 5.5V; IOUT = 100A Load Regulation Ripple Rejection Current Limit IOUT = 100A to 50mA f = up to 1kHz; COUT = 2.2F; CBYP = 0.1F f = 20kHz; COUT = 2.2F; CBYP = 0.1F VOUT = 0V Nominal VOUT tolerance VFB = 0.9*VNOM VOUT > 2.4V; VIN = VOUT + 300mV to 5.5V, ILOAD= 100mA VOUT < 2.4V; VIN = 2.7V to 5.5V, ILOAD= 100mA 20mA < ILOAD < 300mA VFB 0.4V ISW = 150mA VFB = 0.7VFB_NOM ISW = -150mA VFB = 1.1VFB_NOM -2 -3 0.75 +2 +3 1.6 5 % % A nA %/V %/V % % MHz VRMS +2.0 +3.0 % % ppm/C %/V %/V % dB dB mA Conditions Min Typ Max Units
1 1 0.2 0.2
1.5
100 0.6 0.8 2 60
1.8
2.2
80
190
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MIC2800
Electrical Characteristics - LDO1
VIN = VOUTDC/DC; EN1 = VIN; EN2 = GND; COUT1 = 2.2F, IOUT1 = 100A; TJ = 25C, bold values indicate -40C< TJ < +125C; unless noted.
Parameter Conditions Min -2.0 -3.0 300 120 0.17 0.3 500 70 44 30 Typ Max +2.0 +3.0 Units % % mA mA % % mA dB dB VRMS % % % % mA dB dB LOWQ = High (Full Power Mode) Output Voltage Accuracy Variation from nominal VOUT Variation from nominal VOUT; -40C to +125C Output Current Capability VIN > 1.8V VIN > 1.5V Load Regulation IOUT = 100A to 150mA IOUT = 100A to 300mA Current Limit VOUT = 0V Ripple Rejection f = up to 1kHz; COUT = 2.2F; CBYP = 0.1F f = 20kHz; COUT = 2.2F; CBYP = 0.1F Output Voltage Noise COUT = 2.2F; CBYP = 0.1F; 10Hz to 100KHz LOWQ = Low (Light Load Mode) Output Voltage Accuracy Variation from nominal VOUT Variation from nominal VOUT; -40C to +125C Load Regulation IOUT = 100A to 10mA Current Limit Ripple Rejection VOUT = 0V f = up to 1kHz; COUT = 2.2F; CBYP = 0.1F f = 20kHz; COUT = 2.2F; CBYP = 0.1F
1.5 700
350
-3.0 -4.0 0.2 50 85 70 42
+3.0 +4.0 0.5 1.0 125
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MIC2800
Electrical Characteristics - LDO2
VIN = VOUTLDO2 + 1.0V; EN1 = GND; EN2 = VIN; COUT2 = 2.2F; IOUTLDO2 = 100A; TJ = 25C, bold values indicate -40C< TJ < +125C; unless noted.
Parameter Conditions Min -2.0 -3.0 0.02 0.20 0.25 0.40 70 94 142 75 40 550 25 Typ Max +2.0 +3.0 0.3 0.6 Units % % %/V % % % mV mV mV dB dB mA VRMS % % %/V % mV mV dB 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; IOUT = 100A Load Regulation IOUT = 100A to 150mA IOUT = 100A to 200mA IOUT = 100A to 300mA IOUT = 150mA IOUT = 200mA IOUT = 300mA f = up to 1kHz; COUT = 2.2F; CBYP = 0.1F f = 20kHz; COUT = 2.2F; CBYP = 0.1F VOUT = 0V COUT = 2.2F, CBYP =0.1F, 10Hz to 100kHz
1.5
Dropout Voltage
300
Ripple Rejection Current Limit Output Voltage Noise
400
850
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.
-3.0 -4.0 0.02 0.2 22 75 55 85
IOUT = 100A to 10mA IOUT = 10mA f = up to 1kHz; COUT = 2.2F; CBYP = 0.1F f = 20kHz; COUT = 2.2F; CBYP = 0.1F VIN = 2.7V; VOUT = 0V
+3.0 +4.0 0.3 0.6 1.0 35 50
50
125
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. 6. VOUT denotes the highest of the three output voltage plus one volt.
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Typical Characteristics (DC/DC PWM Mode)
DC/DC 1.87VOUT Efficiency
100 95 90 85 80 75 70 65 60 55 50 0 L = 2.2H COUT = 2.2F /LowQ = VIN 100 200 300 400 500 600 OUTPUT CURRENT (mA) 3V 3.6V 4.2V
DC/DC 1.8VOUT Efficiency
100 95 90 85 80 75 70 65 60 55 50 0 L = 2.2H COUT = 2.2F /LowQ = VIN 100 200 300 400 500 600 OUTPUT CURRENT (mA)
1400
DC/DC Current Limit vs. Temperature
3V
3.6V 4.2V
1200 1000 800 600 400 200 0 COUT = 2.2F CBYP = 0.1F /LowQ = VIN EN1 = EN2 = VIN 20 40 60 80 TEMPERATURE (C)
1000 950 900 850 800 750 700 650 600 550
DC/DC Enable Threshold vs. Supply Voltage
100 95 90 85 80 75 70 65 60
DC/DC Turn-On Delay vs. Supply Voltage
ON OFF
500 2.7
COUT = 2.2F /LowQ = VIN 3.4 4.1 4.8 5.5 SUPPLY VOLTAGE (V)
55 50 2.7
COUT = 2.2F /LowQ = VIN 3.2 3.7 4.2 4.7 5.2 SUPPLY VOLTAGE (V)
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MIC2800
Typical Characteristics (DC/DC LowQ Mode)
60 50 40 30 20 IOUT = 50mA 10 VOUT = 1.8V COUT = 2.2F /LowQ = GND 0 0.01 0.1 1 10 100 1,000 FREQUENCY (kHz) 3.6V
Power Supply Rejection Ratio (Input Voltage)
4.2V
80 70 60 50 40 30
Power Supply Rejection Ratio (Output Current)
0A
100 80
LDO Current Limit vs. Supply Voltage
100A 50mA
60 40 20 0 2.7 COUT = 2.2F /LowQ = GND 3.4 4.1 4.8 5.5 SUPPLY VOLTAGE (V)
20 VIN = 3.6V VOUT = 1.8V 10 COUT = 2.2F /LowQ = GND 0 0.01 0.1 1 10 100 1,000 FREQUENCY (kHz)
1.90 1.89
LDO Output Voltage vs. Output Current
10
DC/DC LowQ Mode Output Noise Spectral Density
1 1.88 1.87 1.86 1.85 1.84 VIN = 3.6V VOUT = 1.87V COUT = 2.2F /LowQ = GND 10 20 30 40 50 60 70 80 90 OUTPUT CURRENT (mA) 0.1 0.01 VIN = 4.2V VOUT = 1.87V COUT = 2.2F /LowQ = GND 0.001 0.01 0.1 1 10 100 1,000 10,000 FREQUENCY (kHz)
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Micrel, Inc.
MIC2800
Typical Characteristics (LDO1, LDO2)
100
Power Supply Rejection Ratio (LDO1 LowQ Mode)
80 70
Power Supply Rejection Ratio (LDO1 Normal Mode)
-90 -80 -70
Power Supply Rejection Ratio (LDO2 LowQ Mode)
50mA 100A 10mA
90 80 70 60 50 40 50mA 100A
60 50 40 30
50mA 150mA
100A
-60 -50 -40
30 VIN = 4.2V VOUT = 1.2V 20 COUT = 2.2F 10 /LowQ = GND CBYP = 0.1F 0 0.01 0.1 1 10 100 1,000 FREQUENCY (kHz)
VIN = 4.2V 20 VOUT = 1.2V COUT = 2.2F 10 /LowQ = VIN CBYP = 0.1F 0 0.01 0.1 1 10 100 1,000 FREQUENCY (kHz)
-30 VIN = 4.2V = 2.8V V -20 COUT = 2.2F OUT -10 /LowQ = VIN CBYP = 0.01F 0 0.01 0.1 1 10 100 1,000 FREQUENCY (kHz)
100
Power Supply Rejection Ratio (LDO2 Normal Mode)
100A 300mA
3.00 2.95 2.90 2.85 2.80 2.75 2.70 2.65 2.60 2.55 2.50
(LDO2) Output Voltage vs. Temperature
70 65 60 55 50
Ground Current vs. Temperature
100A 300mA VIN = VOUT + 1V 100mA VOUT = 2.8V COUT = 2.2F CBYP = 0.1F /LowQ = VIN EN1 = GND EN2 = VIN 20 40 60 80 TEMPERATURE (C)
90 80 70 60
150mA 50 50mA 40 30 VIN = 4.2V VOUT = 1.2V 20 COUT = 2.2F 10 /LowQ = VIN CBYP = 0.01F 0 0.01 0.1 1 10 100 1,000 FREQUENCY (kHz)
VIN = VOUT + 1V VOUT = 2.8V COUT = 2.2F CBYP = 0.1F EN1 = GND EN2 = VIN 20 40 60 80 TEMPERATURE (C)
45 40 35 30
70
Ground Current vs. Output Current
140 120
(LDO2) Dropout Voltage vs. Output Current
60
100 80 60 VIN = 2.8V VOUT = 2.8V COUT = 2.2F CBYP = 0.1F 50 100 150 200 250 300 OUTPUT CURRENT (mA) 40 20 0 0 VOUT = 2.8V COUT = 2.2F CBYP = 0.1F /LowQ = VIN 50 100 150 200 250 300 OUTPUT CURRENT (mA)
0.20 VOUT = 2.8V 0.18 COUT = 2.2F 0.16 CBYP = 0.1F /LowQ = VIN 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00
(LDO2) Dropout Voltage vs. Temperature
300mA
50
150mA 100mA 50mA
40
20mA
30 0
20 40 60 80 TEMPERATURE (C)
Dropout Chararcteristics
3.0 COUT = 2.2F CBYP = 0.1F /LowQ = VIN 100mA 2.5 150mA 300mA 0.1 10
LDO1 Output Noise Spectral Density
10
LDO2 Output Noise Spectral Density
1
1
0.1 VIN = 4.2V 0.01 VOUT = 2.8V COUT = 2.2F CBYP = 0.1F /LowQ = VIN 0.001 0.01 0.1 1 10 100 1,000 10,000 FREQUENCY (kHz)
2.0 1.5
2.0 2.5 3.0 SUPPLY VOLTAGE (V)
3.5
VIN = 4.2V 0.01 VOUT = 1.2V COUT = 2.2F CBYP = 0.1F /LowQ = VIN 0.001 0.01 0.1 1 10 100 1,000 10,000 FREQUENCY (kHz)
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MIC2800
Functional Characteristics
DC/DC Load Transient PWM Mode
VIN = VOUT + 1V COUT = 2.2F Output Voltage AC Coupled (100mV/div) CBYP = 0.01F /LowQ = VIN
Input Voltage (1V/div)
DC/DC Line Transient PWM Mode
VOUT = 1.8V
VIN = VOUT + 1V VOUT = 1.87V COUT = 2.2F CBYP = 0.01F
Output Voltage AC Coupled (100mV/div)
Output Current (100mA/div)
400mA
/LowQ = VIN IOUT = 100mA
10mA
Time (20s/div)
Time (20s/div)
Enable Transient PWM Mode
Enable Voltage (500mV/div) Output Voltage (500mV/div)
VIN = 3.6V VOUT = 1.8V COUT = 2.2F CBYP = 0.01F /LowQ = VIN IOUT = 300mA Time (40s/div)
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MIC2800
Functional Characteristics
DC/DC Load Transient LowQ Mode
VIN = VOUT + 1V 50mA Output Current (20mA/div) COUT = 2.2F CBYP = 0.01F /LowQ = GND
Input Voltage (1V/div)
DC/DC Line Transient LowQ Mode
VOUT = 1.8V
VIN = VOUT + 1V VOUT = 1.87V COUT = 2.2F CBYP = 0.01F /LowQ = GND
100A
Output Voltage AC Coupled (20mV/div)
Output Voltage AC Coupled (50mV/div)
IOUT = 10mA
Time (10s/div)
Time (20s/div)
Enable Transient LowQ Mode
Supply Voltage & Enable Voltage (2V/div) Output Voltage (500mV/div)
VIN = EN1 = 3.8V VOUT = 1.8V COUT = 2.2F CBYP = 0.01F /LowQ = GND IOUT = 100A Time (20s/div)
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MIC2800
Functional Characteristics
LDO2 Load Transient Normal Mode
LDO2 Load Transient LowQ Mode
Output Voltage AC Coupled (100mV/div)
Output Voltage AC Coupled (50mV/div)
VIN = 3.6V VOUT = 2.8V 300mA COUT = 2.2F CBYP = 0.01F
VIN = VOUT + 1V VOUT = 2.8V COUT = 2.2F CBYP = 0.01F 50mA /LowQ = GND
Output Current (100mA/div)
Output Current (25mA/div)
/LowQ = VIN
100A
100A
Time (4s/div)
Time (200s/div)
LDO2 Line Transient Normal Mode
LDO2 Line Transient LowQ Mode
Input Voltage (1V/div)
5.5V VIN = VOUT + 1V 4V VOUT = 1.87V COUT = 2.2F CBYP = 0.01F /LowQ = VIN
Input Voltage (1V/div)
5.5V VIN = VOUT + 1V VOUT = 1.87V COUT = 2.2F CBYP = 0.01F /LowQ = GND IOUT = 10mA
4V
Output Voltage AC Coupled (50mV/div)
IOUT = 100mA
Output Voltage AC Coupled (50mV/div)
Time (20s/div)
Time (40s/div)
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MIC2800
Functional Characteristics
DC/DC LowQ Mode to PWM Mode Transition
DC/DC PWM Mode to LowQ Mode Transition
LowQ Voltage (1V/div)
LowQ Voltage (1V/div)
VIN = VOUT + 1V VOUT = 1.8V COUT = 2.2F
VIN = VOUT + 1V VOUT = 1.8V Output Voltage AC Coupled (50mV/div)
Output Voltage AC Coupled (50mV/div)
COUT = 2.2F CBYP = 0.01F IOUT = 100A
CBYP = 0.01F IOUT = 50mA
Time (100s/div)
Time (100s/div)
DC/DC PWM Waveform
VIN = 4V VOUT = 1.8V COUT = 2.2F CBYP = 0.01F /LowQ = VIN L = 2.2H
Output Voltage AC Coupled (10mV/div)
LowQ Voltage (2V/div)
Time (400s/div)
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MIC2800
Functional Characteristics
ESR vs. Load LDO
ESR vs. Load LDO1
100
100
10 STABLE AREA 1
10 STABLE AREA 1
0.1 0
50 100 150 OUTPUT CURRENT (mA)
0.1 0
50 100 150 OUTPUT CURRENT (mA)
100
ESR vs. Load LDO2
10 STABLE AREA 1
0.1 0
50 100 150 OUTPUT CURRENT (mA)
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MIC2800
Functional Diagram
VIN VIN CBIAS EN1 _____ LOWQ
DC to DC
LDO SW FB
LDO1 EN2 LDO2
VOUT1 VOUT2
CBYP
Reference and Quick Start
POR
POR
PGND
SGND
CSET
MIC2800 Fixed Block Diagram
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M9999-061406 (408) 955-1690
Micrel, Inc.
MIC2800 LDO1 Regulated output voltage of LDO1. Power is provided by the DCDC switching regulator. Recommended output capacitance is 2.2F. LDO2 Regulated output voltage of LDO2. Power is provided by VIN. Recommended output capacitance is 2.2F. EN Both enable inputs are active high, requiring 1.0V for guaranteed operation. EN1 provides logic control of both the DCDC regulator and LDO1. EN2 provides logic control for LDO2 only. The enable inputs are CMOS logic and cannot be left floating. The enable pins provide logic level control of the specified outputs. When both enable pins are in the off state, supply current of the device is greatly reduced (typically <1A). When the DCDC 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 either 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 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 IQ of 20A. 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 buck 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 10mA. BIAS The BIAS pin supplies the power to the internal control and reference circuitry. The bias is powered from AVIN through an internal 6 resistor. A small 0.1F capacitor is recommended for bypassing.
Application Notes
The MIC2800 is a digital power management IC with a single integrated buck regulator and two independent low dropout regulators. LDO1 is a 300mA low dropout regulator that is using power supplied by the on board buck regulator. LDO2 is a 300mA low dropout regulator using the supply from the input pin. The buck regulator is a 600mA PWM power supply that utilizes a /LOWQ light load mode to maximize battery efficiency in 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, drawing only 20A of operating current. This allows the output to be regulated through the LDO output, 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, 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 MIC2800 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. VIN Two input voltage pins provide power to the switch mode regular and LDO2 separately. The LDO1 input voltage is provided by the DC/DC LDO pin. VIN provides power to the LDO section and the bias through an internal 6 resistor. Both VIN pins must be tied together. For the switch mode regulator VIN provides power to the MOSFET along with current limiting sensing. 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 layout recommendations. LDO The LDO pin is the output of the linear regulator and should be connected to the output. In /LOWQ mode (/LOWQ <0.2V), the LDO provides the output voltage. In PWM mode (/LOWQ >1V) the LDO pin provides power to LDO1.
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Micrel, Inc. FB Connect the feedback pin to VOUT. 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. Refer to the layout considerations for more details. 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. Refer to the layout considerations for more details. CSET The SET 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 micro seconds is equal to the Cset in picofarads. POR Delay (s) = CSET (pF) CBYP The internal reference voltage can be bypassed with a capacitor to ground to reduce output noise and increase power supply rejection (PSRR). A quick-start feature allows for quick turn-on of the output voltage. The recommended nominal bypass capacitor is 0.1F, but it can be increased, which will also result in an increase to the start-up time. Output Capacitor LDO1 and LDO2 outputs require a 2.2F ceramic output capacitor for stability. The DC/DC switch mode regulator
MIC2800 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. X7R/X5R dielectric-type ceramic capacitors are recommended because of their temperature performance. 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. Input Capacitor A minimum 1F ceramic is recommended on the VIN pin for 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 layout recommendations for proper layout of the input capacitor. Inductor Selection The MIC2800 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 + 2x f xL
IPK = IOUT
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M9999-061406 (408) 955-1690
Micrel, Inc.
MIC2800
PCB Layout
Top Layer
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M9999-061406 (408) 955-1690
Micrel, Inc.
MIC2800
Bottom Layer
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M9999-061406 (408) 955-1690
Micrel, Inc.
MIC2800
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.
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M9999-061406 (408) 955-1690

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