MIC2111B Datasheet, PDF (18/35 Pages) Micrel Semiconductor – High-Performance, Multi-Mode, Step-Down Controller

Micrel, Inc.
VCC Undervoltage Lockout (UVLO)
The MIC2111B operates from a single 3.3V or 5V supply
and has only 2mA of quiescent current. When bias
voltage at V_CC is less than the under-voltage lockout
(UVLO) level of 2.85V, HS will be high impedance to
drive both MOSFETs to tri-state. UVLO has 100mV
hysteresis to avoid an undesirable turn-on. If the same
supply voltage is used for the power module and the
MIC2111B, it is recommended to use a series RC filter
(1Ω and 1µF) for MIC2111B bypassing.
Enable/Disable (EN) Control
The precision EN pin is used to enable or disable the
MIC2111B. The typical threshold is 1.2V. When the
voltage at EN rises above the threshold, the controller is
enabled and starts normal operation after initialization of
the internal oscillator, references, current-limit settings,
and the soft-start period. The MIC2111B has initialization
delay of 250µs before the PWM output starts.
When the voltage at EN drops 100mV or more
(hysteresis) below the threshold voltage, then the internal
controller circuits in the MIC2111B are turned off. It is
possible to use the EN pin for sequencing multiple power
supplies along with power-good (PG) pin. Do not float the
EN pin. An external RC delay may be added to achieve
sequencing.
Power Good (PG)
The power-good (PG) pin is an open-drain output.
External pull-up resistance is required between PG and
an external voltage. When the feedback voltage, V_FB,
rises above the PG threshold the PG output is pulled high
after a delay of 200μs (contact Micrel for other PG
delays).
Bi-Directional Fault Communication (FAULTb)
The MIC2111B adopts Micrel’s proprietary fault
(FAULTb) communication protocol. There are multiple
system faults possible in a high-current environment. The
MIC2111B features internal pull-up of 100kΩ between the
VCC and FAULTb pin.
MIC2111B
Soft-Start/Soft-Stop (SS)
The MIC2111B has digital soft-start/soft-stop (SS) to
avoid high inrush current in the input supply lines. Soft-
start time can be programmed with an external resistor
connected from the SS pin to GND. Table 3 illustrates
resistor values and soft start time. Soft-stop time is the
same as the programmed soft-start time (contact Micrel
for instructions on enabling soft-stop).
Table 3. Soft-Start Programming
E96
Range
Resistance
Soft-Start
E96
Range
Resistance
6.19kΩ
64µs
105kΩ
19.1kΩ
128µs
118kΩ
30.9kΩ
256µs
130kΩ
44.2kΩ
512µs
143kΩ
56.2kΩ
768µs
154kΩ
68.1kΩ
1024µs
169kΩ
80.6kΩ
1536µs
182kΩ
93.1kΩ
2048µs
Open
Soft-Start
3072µs
4096µs
6144µs
8192µs
16384µs
24576µs
32768µs
2048µs
October 13, 2015
18
Revision 2.1