MIC7401 Datasheet, PDF (25/68 Pages) Micrel Semiconductor – Configurable PMIC, Five-Channel Buck Regulator plus One-Boost with HyperLight Load®, I2C Control, and Enable

Micrel, Inc.
Functional Description
The MIC7401 is one of the industry’s most-advanced
PMIC designed for solid state drives (SSD) on the market
today. It is a multi-channel solution which offers software
configurable soft-start, sequencing, and digital voltage
control (DVC) that minimizes PC board area. These
features usually require a pin for programming. However,
this approach makes the IC larger by increasing pin
count, and also increases BOM cost due to the external
components.
The following is a complete list of programmable
features:
• Buck output voltage (0.8V – 3.3V/50mV steps)
• Boost output voltage (7.0V – 14V/ 200mV steps)
• Power-on-reset (2.25V – 4.25V/50mV steps)
• Power-on-reset delay (5ms – 160ms/5ms steps)
• Power-up sequencing (6 time slots)
• Power-up sequencing delay (0ms – 7ms/1ms steps)
• Soft-start (4µs – 1024µs per step)
• Buck current limit threshold
− (1.1A to 6.1A/0.5A steps)
• Boost current limit threshold
− (1.76A to 2.6A/0.12A steps)
• Boost pull-down (37mA to 148mA/37mA steps)
• Buck pull-down (90Ω)
• Buck standby output voltage programmable
• Boost standby output voltage programmable
• Global power good masking
These features give the system designer the flexibility to
customize the MIC7401 for their application. For
example, V_OUT1 current limit can be programmed to 4.1A
and V_OUT2 can be set to 1.1A. These outputs can be
programmed to come up at the same time or 2.0ms
apart. In addition, in power-saving standby mode, the
outputs can either be turned off or programmed to a
lower voltage. With this programmability the MIC7401
can be used in multiple platforms.
The MIC7401 buck regulators are adaptive on-time
synchronous step-down DC-to-DC regulators. They are
designed to operate over a wide input voltage range from
2.4V to 5.5V and provide a regulated output voltage at up
to 3.0A of output current. An adaptive on-time control
scheme is employed to obtain a constant switching
frequency and to simplify the control compensation. The
device includes an internal soft-start function which
reduces the power supply input surge current at start-up
by controlling the output voltage rise time.
MIC7401
The MIC7401 has a current-mode boost regulator that
can deliver up to 200mA of output current and only
consumes 70µA of quiescent current. The 2.0MHz
switching frequency allows small chip inductors to be
used. Programmable overcurrent sensing protects the
boost from overloads and an output disconnect switch
opens to protect against a short-circuit condition. Soft-
start is also programmable and controls both the rising
and falling output.
Programmable Buck Soft-Start Control
The MIC7401 soft-start feature forces the output voltage
to rise gradually, which limits the inrush current during
start-up. A slower output rise time will draw a lower input
surge current. The soft-start time is based on the least
significant bit (LSB) of an internal DAC and the speed of
the ramp rate, as shown in Figure 1. This illustrates the
soft-start waveform for all five synchronous buck
converters. The initial step starts at 150mV and each
subsequent step is 50mV.
Figure 1. Buck Soft-Start
The output ramp rate (t_RAMP) is set by the soft-start
registers. Each output ramp rate can be individually set
from 4µs to 1024µs, see Table 1 for details.
March 16, 2015
25
Revision 1.0