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April 1997
ML4890
High Efficiency, Low Ripple Boost Regulator
GENERAL DESCRIPTION
The ML4890 is a high efficiency, PFM (Pulse Frequency Modulation), boost switching regulator connected in series with an integrated LDO (Low Dropout Regulator) that incorporates “Silent Switcher™” technology. This technique incorporates a patented tracking scheme to minimize the voltage drop across the LDO and increase the total efficiency of the regulator beyond that which can be obtained by using a discrete external LDO regulator. The ML4890 is designed to convert single or multiple cell battery inputs to regulated output voltages for integrated circuits and is ideal for portable communications equipment that cannot tolerate the output voltage ripple normally associated with switching regulators. An integrated synchronous rectifier eliminates the need for an external Schottky diode and provides a lower forward voltage drop, resulting in higher conversion efficiency.
FEATURES
s s
Incorporates “Silent Switcher™” technology to deliver very low output voltage ripple (typically 5mV) Guaranteed full load start-up and operation at 1.0V input and low operating quiescent current (<100µA) for extended battery life Pulse Frequency Modulation and internal synchronous rectification for high efficiency Minimum external components Low ON resistance internal switching MOSFETs 5V, 3.3V, and 3V output versions
s s s s
BLOCK DIAGRAM
L1
*CIN
VIN
C2 1 VL 6 5 VBOOST
VBAT 7
SHDN VOUT 4 BOOST CONTROL FEEDBACK LDO CONTROL C1 VOUT +
2
VREF
3 FROM POWER MANAGEMENT
GND
PWR GND
8
–
Patent Pending *Optional
1
ML4890
PIN CONNECTION
ML4890-5/-3/-T 8-Pin SOIC (S08)
VIN VREF GND VOUT
1 2 3 4
8 7 6 5
PWR GND SHDN VL VBOOST
TOP VIEW
PIN DESCRIPTION
PIN NO. PIN NO.
NAME
FUNCTION
NAME
FUNCTION
1 2 3 4
VIN VREF GND VOUT
Battery input voltage 200mV reference output Analog signal ground LDO linear regulator output
5 6 7
VBOOST VL SHDN
Boost regulator output for connection of an output filter capacitor Boost inductor connection Pulling this pin high shuts down the regulator, isolating the load from the input
8
PWR GND Return for the NMOS boost transistor
2
ML4890
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. VBOOST ........................................................................ 7V Voltage on Any Other Pin ... GND –0.3V to VBOOST +0.3V Peak Switch Current (IPEAK) .......................................... 1A Average Switch Current (IAVG) ............................... 500mA LDO Output Current ............................................. 250mA Junction Temperature .............................................. 150°C Storage Temperature Range .................... –65°C to +150°C Lead Temperature (Soldering 10s) .......................... +260°C Thermal Resistance (θJA) Plastic SOIC .................................................... 110°C/W
OPERATING CONDITIONS
Temperature Range ML4890CS-X ............................................ 0°C to +70°C ML4890ES-X ......................................... –20°C to +70°C VIN Operating Range ML4890CS-X ................................................ 1.0V to 6V ML4890ES-X ................................................. 1.1V to 6V
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, VIN = Operating Voltage Range, TA = Operating Temperature Range. (Note 1)
PARAMETER Supply VIN Current VIN = 6V SHDN = high VOUT Quiescent Current VL Quiescent Current Reference Output Voltage (VREF) PFM Regulator Pulse Width (TON) LDO DC Output Voltage (VOUT) ML4890-5 ML4890-3 ML4890-T Load Regulation ML4890-5 VBOOST = VOUT + 0.5V, IOUT < 200mA VBOOST = VOUT + 0.5V, IOUT < 100mA VBOOST = VOUT + 0.5V, IOUT < 80mA See Figure 1 VIN = 1.2V, IOUT < 7mA VIN = 2.4V, IOUT < 50mA VIN = 1.2V, IOUT < 14mA VIN = 2.4V, IOUT < 75mA VIN = 1.2V, IOUT < 15mA VIN = 2.4V, IOUT < 60mA See Figure 1 VIN = 1.2V, IOUT < 7mA VIN = 2.4V, IOUT < 50mA VIN = 1.2V, IOUT < 14mA VIN = 2.4V, IOUT < 75mA VIN = 1.2V, IOUT < 15mA VIN = 2.4V, IOUT < 60mA 5 4.85 3.2 2.91 4.85 4.85 3.2 3.2 2.91 2.91 5.0 3.3 3.0 5.0 5.0 3.3 3.3 3.0 3.0 5.15 3.4 3.09 5.15 5.15 3.4 3.4 3.09 3.09 300 500 300 500 300 500 V V V V V V V V V mV mV mV mV mV mV mVP-P 4.5 5 5.5 µs 0 < IPIN2 < –5µA, 195 200 205 mV VBOOST = VOUT + 0.5V 60 15 8 75 25 10 1 µA µA µA µA CONDITIONS MIN TYP. MAX UNITS
ML4890-3 ML4890-T Dropout Voltage ML4890-5
ML4890-3 ML4890-T Output Ripple Shutdown SHDN Threshold SHDN Bias Current
Note 1:
0.5 –100
0.8
1.0 100
V nA
Limits are guaranteed by 100% testing, sampling, or correlation with worst case conditions.
3
ML4890
33µH (Sumida CD54)
ML4890
VIN 100µF VIN VREF 1µF GND VOUT PWR GND SHDN VL VBOOST 33µF
IOUT VOUT 100µF
Figure 1. Applicati.