MIC2169BMM Micrel Inc, MIC2169BMM Datasheet - Page 12

• Manufacturer Part Number: MIC2169BMM
• Description: IC CTRLR PWM SYNC BUCK 10-MSOP
• Manufacturer: Micrel Inc

Specifications of MIC2169BMM

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 550kHz
• Duty Cycle: 92%
• Voltage - Supply: 3 V ~ 14.5 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Frequency-max: 550kHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Total Open-Loop Response
The open-loop response for the MIC2169 controller is easily
obtained by adding the power path and the error amplifi er
gains together, since they already are in Log scale. It is
desirable to have the gain curve intersect zero dB at tens of
kilohertz, this is commonly called crossover frequency; the
phase margin at crossover frequency should be at least 45°.
Phase margins of 30° or less cause the power supply to have
substantial ringing when subjected to transients, and have
little tolerance for component or environmental variations.
Figures 9 and 10 show the open-loop gain and phase margin.
It can be seen from Figure 9 that the gain curve intersects
the 0dB at approximately 50kHz, and from Figure 10, that at
50kHz, the phase shows approximately 50° of margin.
M9999-032409
2 5.856
270
Figure 8. Error Amplifi er Phase Curve
200
220
240
260
0
0
00
. 0
3
f
. 0
4
. 0
5
000000
. 0
6
12
269.097
42.933
71.607
360
250
300
350
100
50
50
Figure 10. Open-Loop Phase Margin
0
10
10
100
100
Figure 9. Open-Loop Gain Margin
100
1 . 10
3
1 . 10
3
1 . 10
f
f
1 . 10
4
4
1 . 10
1 . 10
5
5
1000000
1000000
March 2009
1 . 10
1 . 10
6
6