MB3789 Fujitsu, MB3789 Datasheet
MB3789
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MB3789 Summary of contents
Page 1
... The MB3789 incorporates two error amplifiers which can be used respectively for voltage control and current control, allowing the IC to serve as a DC/DC converter with current regulating functions. The MB3789 is the ideal IC for supplying power to the back-lighting fluorescent tube for a liquid crystal display (LCD) device such as a camera-integrated VTR. ...
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... MB3789 PIN ASSIGNMENT REF C T SYNC SCP *1 FB1 *1 IN1 *1 + IN1 2 (TOP VIEW (FPT-16P-M05) *1: Pins on error amplifier 1 *2: Pins on error amplifier 2 GND OUT DTC *2 FB2 *2 IN2 *2 + IN2 ...
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... Dead time control pin O Totem-pole output pin Sawtooth waveform frequency setting capacitor/resistor connection — pin I External sync signal input pin — Reference power supply, control circuit power-supply pin — Output circuit power-supply pin O Reference voltage output pin — Ground pin MB3789 3 ...
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... MB3789 BLOCK DIAGRAM Error amp. 1 +IN1 8 IN1 7 FB1 6 Error amp. 2 +IN2 9 IN2 10 FB2 11 12 DTC 8 A SCP comparator 1 1.25 V SCP comparator 1.1 V Reference Power voltage ON/OFF 2 V REF supply circuit 16 GND 4 PWM comparator 4 A 1.25 V SCP comparator REF 1 ...
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... An arbitrary loop gain can be set by connecting a feedback resistor and capacitor from the error amplifier output pin to the inverting input pin, enabling stable phase compensation to the system. The MB3789 can make a current-regulated DC/DC converter using the two internal error amplifiers respectively for voltage control and current control. ...
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... MB3789 2. Protection Functions (1) Timer-latch short-circuit protection circuit SCP comparator 1 detects the output voltage levels of error amplifiers 1 and 2. When the output voltage level of both of the two error amplifiers reaches 1.25 V, the timer circuit is actuated to start charging the external protection-enable capacitor connected to the SCP pin (pin 5). ...
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... OR V — –0 – 4700 pF 4700 pF O– R — — 470 T f — OSC T — –30 OP MB3789 (Ta = +25 C) Rating Unit Max 20 V 440* mW +85 C +125 C (Ta = +25 C) Value Unit Typ Max 3.0 5 — 6 –30 — ...
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... MB3789 ELECTRICAL CHARACTERISTICS Parameter Output voltage Output voltage temperature Reference variation voltage block Input stability Load stability Short output current Under Threshold voltage voltage lockout Hysteresis width protection circuit Reset voltage ( Charge current Soft start block Threshold voltage Threshold voltage ...
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... Duty cycle = 100% T100 I — IN+ I — IN– 2000 pF 4700 2000 pF 4700 — — CC MB3789 ( + Value Unit Min Typ Max — — — — 100 nA –200 –30 — nA –0.2 — ...
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... MB3789 TYPICAL CHARACTERISTICS Power supply current vs. power supply voltage characteristics 2.4 2.0 1.6 1.2 0.8 0 Power supply voltage V Reference voltage vs. power supply voltage characteristics 5.0 4.0 3.0 2.0 1 Power supply voltage V Sawtooth waveform maximum amplitude voltage vs. timing capacitance characteristics (With 1.4 1.2 1.0 0.8 0.6 0.4 0 Timing capacitance C ...
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... Ambient temperature Measurement circuit for gain-frequency characteristics and phase-frequency characteristics 2.5 V 2.5 V 180 4 4 4.7 k 4.7 k 180 10 M MB3789 0 Variable SYNC = GND 100 k 500 ...
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... MB3789 (Continued) Duty vs. DTC pin voltage characteristics 100 1500 SYNC = GND 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 DTC pin voltage Vdt (V) Power comsumption vs. ambient temperature characteristics 500 440 400 300 200 100 Ambient temperature ...
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... The oscillation frequency can be set by connecting the timing resistor (R terminal (pin 3) . Oscillation frequency : f OSC 78000 f ( OSC Z C (pF OUT V REF + V = OUT REF V = OUT OUT ( MB3789 ( OUT ( REF )) OUT ) and the timing capacitor to the ...
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... MB3789 CONNECTION FOR OUTPUT CONTROL WITH ONE ERROR AMPLIFIER The MB3789 can make up a system using only one of the two error amplifiers. In this case, connect the +IN and –IN pins of the unused error amplifier to the V When V – 1 divide the V CC REF ...
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... R constants SYNC Leave “open” or connect to GND conditions so that the oscillation frequency 10% lower than the T C SYNC External sync signal R T MB3789 ) to the C pin (pin 3) and and resistor ( the C pin ...
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... MB3789 SETTING THE DEAD TIME When the device is set for step-up inverting output based on the flyback method, the output transistor is fixed to a full-ON state (ON duty = 100%) when the power supply is turned on. To prevent this problem, you may determine the voltage at the DTC pin (pin 12) from the V time (maximum ON-duty period) as shown in Figure 7 below ...
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... Figure 9 Soft start/short-circuit detection circuit 2 1 100% 50 Soft start 0 Figure 10 SCP pin operating waveform 1.25 V SCP comparator 1 latch 5 SCP C PE Output short-circuit Time t (s) MB3789 Output OFF V REF Low input voltage protection circuit Output short-circuit ...
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... MB3789 1. Soft Start To prevent surge currents when the IC is turned on, you can set a soft start by connecting capacitor C SCP pin (pin 5). •Softstart time(ts): Time required up to duty cycle t ( Protection from short circuit SCP comparator 1 always compares the output voltage levels at error amplifiers 1 and 2 with the 1.25 V reference voltage ...
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... C t (Max) [pF – 2 (Max): Maximum ON duty time level. It can therefore drive the MOS FET at a higher threshold CBS OUT OUT c d MB3789 1 CC External MOS FET 19 ...
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... MB3789 2. Connection with no bootstrap capacitor Connect the CB pin (pin 13) and V Note: Under a condition of “V the external MOS FET cannot be driven sufficiently External MOS FET threshold voltage th Figure 13 Connection with no bootstrap capacitor connected 20 2 pin (pin 14) as shown in Figure 13 ...
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... CBS V OUT OFF Time CBS (output unit supply current). d MB3789 ) at both ends of the bootstrap capacitor ~ rises and V CBS CC OUT (output unit supply current 100 21 ...
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... MB3789 EQUIVALENT SERIES RESISTANCE OF SMOOTHING CAPACITOR AND SYSTEM STA- BILITY The equivalent series resistance (ESR) value of a smoothing capacitor for the DC/DC converter largely affects the loop phase characteristic. Depending on the ESR value, the phase characteristic causes the ideal capacitor in a high-frequency domain advance the loop phase (as shown in Figures 16 and 17) and thus the system is improved in stability ...
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... -phase characteristic V in this range + REF 180 180 10 k 100 k Figure 19 Gain vs. frequency MB3789 ~ 1 low-ESR semicon electrolytic capacit 220 kHz C OSC GND 23 ...
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... MB3789 OS capacitor gain vs. frequency, phase vs. frequency (DC/DC converter +5 V output 100 Frequency f (Hz) Figure 20 Phase vs. frequency characteristic curves 180 180 100 capacitor kHz C OSC ...
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... MB3789 100 k 10 IN2 10 k 100 k 11 FB2 150 k 12 DTC SYNC 100 4 Synchronous signal 4700 pF 15 OUT GND SCP 1500 pF 4.7 F MB3789 Back light ...
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... The worker must put on a grounding device containing 250 k • Do not apply a negative voltage - Applying a negative voltage of 0 less to an LSI may generate a parasitic transistor, resulting in malfunction. ORDERING INFORMATION Part number MB3789PFV resistors in series. Package 16-pin Plastic SSOP (FPT-16P-M05) ...
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... Details of "A" part "A" 0.13(.005) M 0.50±0.20 (.020±.008) 0.60±0.15 (.024±.006) Dimensions in mm (inches). Note : The values in parentheses are reference values. MB3789 +0.20 1.25 –0.10 (Mounting height) +.008 .049 –.004 0~8 ˚ 0.10±0.10 (Stand off) (.004±.004) ...
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... MB3789 FUJITSU LIMITED All Rights Reserved. The contents of this document are subject to change without notice. Customers are advised to consult with FUJITSU sales representatives before ordering. The information, such as descriptions of function and application circuit examples, in this document are presented solely for the purpose of reference to show examples of operations and uses of Fujitsu semiconductor device ...