MIC3839BMM TR Micrel Inc, MIC3839BMM TR Datasheet - Page 8

• Manufacturer Part Number: MIC3839BMM TR
• Description: IC CTRLR DC/DC PUSH-PULL 10-MSOP
• Manufacturer: Micrel Inc

Specifications of MIC3839BMM TR

• Pwm Type: Voltage/Current Mode
• Number Of Outputs: 1
• Frequency - Max: 1MHz
• Duty Cycle: 50%
• Voltage - Supply: 2 V ~ 14 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Frequency-max: 1MHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: MIC3839BMMTR; MIC3839BMMTR

MIC3838/3839
Functional Diagram
Functional Description
The MIC3838/9 is a high-speed power supply controller with
push-pull output drive capability. MIC3838 has a higher V
turn-on threshold and more hysteresis between V
and turn-off than the MIC3839. The outputs of the controller
operate in a push-pull fashion with a guaranteed dead time
between them. A block diagram of the MIC3838/9 controller
is shown in Figure 1.
MIC3838/3839
Figure 2. Volt Second Clamp and Voltage Feed Forward Circuit
150k
13k
V
IN
V
V
= 36V to 75V
MAX
MAX
at Ramp Input = 1.5V
at I
330pF
LIM
50k
4.5k
Input = 0.5V
Figure 1. MIC3838 Block Diagram
330pF
DD
turn-on
DD
8
V
The oscillator and output gate drive signals are disabled
when V
output drivers eliminates glitching or random pulsing during
the start-up sequence. The oscillator is enabled when V
applied and reaches the turn-on threshold. The V
parator also turns off the internal soft-start discharge FET,
slowly bringing up the COMP pin voltage.
The V
clamp voltage, the V
current draw of the IC. IDD currents greater than 20mA may
cause excessive power dissipation in the MIC3838/9.
MIC3838
DD
V
0.75V
0.5V
COMP
and Turn-on Sequence
DD
DD
pin is internally clamped. As V
is lower than the turn on threshold. Circuitry in the
Oscillator
PWM
Comparator
Peak Current
Comparator
Over Current
Comparator
DD
current will increase over the normal
DD
approaches this
April 2005
DD
Micrel
com-
DD
is