mic3808 Micrel Semiconductor, mic3808 Datasheet
mic3808
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mic3808 Summary of contents
Page 1
... The high-speed internal 4MHz error amplifier allows MIC3808/9 operation up to 1MHz. The MIC3808 has a turn-on threshold of 12.5V whereas the MIC3809 has a lower turn-on threshold of 4.3V. Both devices are available in SOP-8 and MSOP-8 package options with an operating range of – ...
Page 2
... Pin Function COMP is the output of the error amplifier and the input of the PWM com- parator. The error amplifier in the MIC3808 is a true low-output impedance, 4MHz operational amplifier. As such, the COMP pin can both source and sink current. However, the error amplifier is internally current limited, so that zero duty cycle can be externally forced by pulling COMP to GND ...
Page 3
... MOSFET gate charge (Qg), average OUT current can be calculated from × F, where F is frequency. To OUT prevent noise problems, bypass V to GND with a ceramic capacitor as DD close to the chip as possible. A 1µF decoupling capacitor is recommended. 3 Micrel to GND. DD current DD current DD MIC3808/3809 ...
Page 4
... Over Current Threshold COMP to CS Offset Output Section OUT Low Level I = 100mA OUT High Level I = –50mA, V Rise Time C L Fall Time C L MIC3808/3809 Operating Ratings (Note 1) V Input Voltage (V DD Oscillator Frequency (f Ambient Temperature (T Package Thermal Resistance SOIC-8 (θ DD +0.3V MSOP-8 (θ DD NOT TO EXCEED 6V to GND 22KΩ ...
Page 5
... Parameter measured at trip point of latch with FB at 0V. Note 8. The internal current sink on the CS pin is designed to discharge an external filter capacitor not intended sink path. Note 9. For MIC3808, set V above the start threshold before setting at 10V. DD Note 10. Does not include current in the external oscillator network. ...
Page 6
... V = 10V -40 - 100120140 TEMPERATURE (°C) RC Pin Resistance vs. Deadtime RESISTANCE (kΩ) MIC3808 Current Limit Threshold vs 0.501 0.499 0.497 0.495 0.493 0.491 0.489 (V) DD MIC3808/3809 MIC3809 ...
Page 7
... Supply Current DD vs. Temperature 10V -40 - 100120140 TEMPERATURE (°C) April 2005 Error Ampifier 120 180 160 100 140 80 120 60 100 Magnitude Phase - 10k 100K 1M 10M 10 100 1k FREQUENCY (Hz) 7 Micrel MIC3808/3809 ...
Page 8
... Reference Functional Description The MIC3808 high-speed power supply controller with push-pull output drive capability. MIC3808 has a higher V turn-on threshold and more hysteresis between V and turn-off than the MIC3809. The outputs of the controller operate in a push-pull fashion with a guaranteed dead time between them ...
Page 9
... Front edge blanking In current mode control, a PWM comparator uses the inductor current signal and the error amplifier signal to determine the operating duty cycle. In the MIC3808/9 the signal at the CS pin is level shifted up before it reaches the PWM comparator as shown in Figure 1. This allows operation of the error amplifier and PWM comparator in a linear region. There are two current limit thresholds in the MIC3808/9 ...
Page 10
... If a current sense resistor is used, it’s ground end must is first applied to the be located very close to the ground pin of the MIC3808/ 9 controller. Careful PCB layout is necessary to keep the high current levels in the current sense resistor from running over the low level signals in the controller. ...
Page 11
... MIN 8-Pin MSOP (MM (408) 944-0970 FAX Micrel for any damages resulting from such use or sale. © 2005 Micrel, Incorporated. 11 45° 0.010 (0.25) 0.007 (0.18) 0.050 (1.27) 0.016 (0.40) 0.244 (6.20) 0.228 (5.79) DIMENSIONS: INCH (MM) 0.007 (0.18) 0.005 (0.13) 0.012 (0.03) R 0.039 (0.99) 0.035 (0.89) 0.021 (0.53) http://www.micrel.com WEB Micrel MIC3808/3809 ...