MB3821 Fujitsu Media Devices, MB3821 Datasheet
MB3821
Available stocks
Related parts for MB3821
MB3821 Summary of contents
Page 1
... DC/DC Converter IC With Synchronous Rectifier MB3821 DESCRIPTION The MB3821 is a pulse width modulation (PWM) type 2-channel DC/DC converter IC with synchronous rectification designed for low voltage, high efficiency operation in high precision and high frequency applications, ideal for down conversion. A normal/low-power mode selection is provided, ideal for an internal power supply (3.3V, 5V) in applications with substantial load current variation, such as notebook computers ...
Page 2
... MB3821 PIN ASSIGNMENT GND : 3 CS1 : 4 IN1 : 5 IN FB1 : 6 (CH1) SEL : 7 OUT1 VS1 : 9 OUT CB1 : 10 OUT2 GND( (TOP VIEW REF 23 CSCP 21 : CS2 20 : IN2 19 : FB2 18 : CTL 17 : OUT1 VS2 15 : CB2 14: OUT2 2 13 :VB (FPT-24P-M03) IN (CH2) OUT ...
Page 3
... Channel 2 error amplifier inverted input pin. 21 CS2 — Channel 2 soft start capacitance connection pin(also channel control). 22 CSCP — Timer-latch short circuit protection capacitance connection pin — Reference power supply, control circuit power supply pin Reference voltage output pin. REF MB3821 Descriptions 3 ...
Page 4
... MB3821 BLOCK DIAGRAM 1 1 FB1 6 Error Amp. IN1 5 CS1 4 1.26 V < CH1 > FB2 19 Error Amp. IN2 20 CS2 21 1.26 V < CH2 > SCP Comp. 1 CSCP 22 S Latch 4 PWM Comp.1 PWM Comp.2 (40 mV) PWM Comp.1 PWM Comp.2 (40 mV) 2.1 V bias R UVLO OSC SEL CB1 ...
Page 5
... Duty — — T SEL 0 V (Normal mode) f OSC SEL 5 V (Low power mode) C — — SCP C — — MB3821 Rating Unit Min. Max. — — — — 500 mA — 740 125 C Value Unit Min ...
Page 6
... MB3821 ELECTRICAL CHARACTERISTICS Parameter Symbol Output voltage Output voltage temperature variation Input stability Load stability Short-circuit output current Threshold voltage Hysteresis width Reset voltage Charge current Input standby voltage Threshold voltage Input source current Short detection time Input standby voltage Input latch voltage ...
Page 7
... IC standby mode CTL 5 V CTL I 23 CTL 0 V CCS SEL (Normal mode SEL (Low power mode) MB3821 ( SEL = + Value Unit Min. Typ. Max. 1.235 1.260 1.285 V — 0.5* — % –200 –50 — 100 — ...
Page 8
... MB3821 TYPICAL CHARACTERISTICS Power supply current vs. power supply voltage Power supply voltage V Reference voltage vs. power supply voltage Power supply voltage V Reference voltage vs. ambient temperature 2.0 1.5 1.0 0.5 0.0 0.5 1.0 1.5 2 Ambient temperature Power supply current vs. power supply voltage 2 ...
Page 9
... M Ambient temperature (Hz) OSC Triangular wave oscillator frequency CTL 5 V SEL 100 100 10 n 100 MB3821 CTL (V) SEL CTL 5 V SEL 0 V Upper ...
Page 10
... MB3821 (Continued) Duty vs. oscillator frequency (ch1) 100 100 k Oscillator frequency f Triangular wave oscillator frequency vs. timing resistance 100 Timing resistance R Triangular wave oscillator frequency vs. power supply voltage 250 240 230 ...
Page 11
... Ambient temperature 180 135 135 180 Ambient temperature MB3821 vs. ambient temperature CTL 5 V SEL 500 100 2.52 V 240 2.4 k Error amplifier ...
Page 12
... MB3821 FUNCTIONAL DESCRIPTION 1. DC/DC Converter Function (1) Reference voltage circuit (Ref) The reference voltage circuit generates a temperature-compensated reference voltage ( 2.50 V) using the voltage supplied from the power supply terminal (pin 23). This voltage is used as the reference voltage for the internal circuits of the IC. The reference voltage can also be supplied to an external device from the maximum current of 1mA ...
Page 13
... After the short protection circuit has been activated reset by simply restarting the power supply. (See “METHOD OF SETTING TIME CONSTANT FOR TIMER LATCH SHORT-CIRCUIT PROTECTION CIRCUIT”.) MB3821 13 ...
Page 14
... MB3821 METHOD OF SETTING SOFT START TIME To provide a soft start by preventing current surges at power-on, soft start capacitors (Cs1, Cs2) are connected to both channels, the CS1 pin (pin 4) for CH1 and the CS2 pin (pin 21) for CH2. When the IC is started (when the CTL pin (pin 18) goes to “H” level, and Vcc Q2 and Q3 switch off and the CS1 and CS2 pins begin charging the external soft start capacitors (Cs1, Cs2 ...
Page 15
... TREATMENT WITHOUT USING CS TERMINAL When you do not use the soft start circuit, open the CS1 terminal (pin 4) and CS2 terminal (pin 22). Treatment When Not Using SCP 4 21 CS1 CS2 MB3821 15 ...
Page 16
... MB3821 METHOD OF SETTING TIME CONSTANT FOR TIMER-LATCH SHORT-CIRCUIT PROTECTION CIRCUIT The short detection comparator (SCP comparator) constantly compares the error amplifier output level to the reference voltage. While the switching regulator load conditions are stable on all channels, the short detection comparator output remains at “ ...
Page 17
... Treatment When Not Using SCP Channel Control Method On/off controls for either channel are enabled by setting the CS pins. Setting Conditions CS1 GND GND Open Open 3 GND CSCP CS pin setting Channel output state CS2 CH1 GND OFF Open OFF GND ON Open ON MB3821 22 CH2 OFF ON OFF ON 17 ...
Page 18
... MB3821 METHOD OF SETTING OSCILLATOR FREQUENCY Oscillator Frequency can be set by timing capacitor (C connected to RT pin (pin 2). Oscillator frequency • Normal mode 1000000 f (kHz OSC C (pF • Low power mode 100000 f (kHz OSC C (pF connected to CT pin (pin 1) and timing resistor (R ...
Page 19
... APPLICATION EXAMPLE MB3821 19 ...
Page 20
... MB3821 REFERENCE DATA • Load characteristic Conversion efficiency vs. load current 3.3 V output (5 V output OFF) 100 Vin 500 XCS1 XCS2 0.001 0.005 0.01 0.05 0.1 Load current I • Normal mode Conversion efficiency vs. Input voltage 100 3 ...
Page 21
... XCS1 XCS2 75 SEL = Input voltage Vin (V) MB3821 5 V output (3.3 V output OFF 500 XCS1 XCS2 SEL = ...
Page 22
... After mounting, printed circuit boards should be stored and shipped in conductive bags or containers. • Work platforms, tools, and instruments should be properly grounded. • Working personnel should be grounded with resistance of 250 between body and ground. ORDERING INFORMATION Part number MB3821PFV 22 Package 24-pin plastic SSOP (FPT-24P-M03) ...
Page 23
... NOM "A" +0.10 +0.05 0.22 0.15 –0.05 –0.02 +.004 +.002 .009 .006 –.002 –.001 MB3821 Details of "A" part 0.10±0.10(.004±.004) (STAND OFF) 0 10° 0.50±0.20 (.020±.008) Dimensions in: mm (inches) 23 ...
Page 24
... MB3821 FUJITSU LIMITED For further information please contact: Japan FUJITSU LIMITED Corporate Global Business Support Division Electronic Devices KAWASAKI PLANT, 4-1-1, Kamikodanaka Nakahara-ku, Kawasaki-shi Kanagawa 211-8588, Japan Tel: 81(44) 754-3763 Fax: 81(44) 754-3329 http://www.fujitsu.co.jp/ North and South America FUJITSU MICROELECTRONICS, INC. Semiconductor Division ...