Datasheet

MAX16993 Step-Down Controller with
Dual 2.1MHz Step-Down DC-DC Converters
www.maximintegrated.com
Maxim Integrated │ 12
Detailed Description
The MAX16993 power-management integrated circuit
(PMIC) is a 2.1MHz, multichannel, DC-DC converter
designed for automotive applications. The device includes
one high-voltage step-down controller (OUT1) designed
to run directly from a car battery and two low-voltage step-
down converters (OUT2/OUT3) cascaded from OUT1.
The 2.1MHz, high-voltage buck controller operates with
a 3.5V to 36V input voltage range and is protected from
load-dump transients up to 42V. The high-frequency
operation eliminates AM band interference and reduces
the solution footprint. It can provide an output voltage
between 3.0V and 5.5V set at the factory or with external
resistors. Each device has two frequency options that
are pin selectable: 2.1MHz or a lower frequency based
on factory setting. Available factory-set frequencies are
1.05MHz, 525kHz, 420kHz, or 350kHz. Under no-load
conditions, the device consumes only 30µA of quiescent
current with OUT1 enabled.
The dual buck converters can deliver 1.5A or 3.0A of
load current per output. They operate directly from OUT1
and provide 0.8V to 3.95V output voltage range. Factory
trimmed output voltages achieve ±3% output error over
load, line, and temperature without using expensive
±0.1% resistors. In addition, adjustable output-voltage
versions can be set to any desired values between 0.8V
and 3.6V using an external resistive divider. On-board
low R
DS(ON)
switches help minimize efficiency losses at
heavy loads and reduce critical/parasitic inductance, mak-
ing the layout a much simpler task with respect to discrete
solutions. Following a simple layout and footprint ensures
first-pass success in new designs (see the PCB Layout
Guidelines section).
The device features a SYNC input (see the Synchronization
(SYNC) section and the Selector Guide). An optional
spread-spectrum frequency modulation minimizes radi-
ated electromagnetic emissions due to the switching
frequency, and a factory-programmable synchronization
I/O (SYNC) allows better noise immunity. Additional fea-
tures include a 4ms fixed soft-start for OUT1 and 2.5ms
for OUT2/OUT3, individual RESET_ outputs, overcurrent,
and overtemperature protections. See the Selector Guide
for the available options.
Enable Inputs (EN_)
All three regulators have their own enable input. When
EN1 exceeds the EN1 high threshold, the internal lin-
ear regulator is switched on. When V
SUP
exceeds the
V
SUP,STARTUP
threshold, Buck 1 is enabled and OUT1
starts to ramp up with a 4ms soft-start. Once the Buck 1
soft-start is complete, Buck 2 and Buck 3 can be enabled.
When either Buck 2 or Buck 3 is enabled, the correspond-
ing output ramps up with a 2.5ms soft-start. When an
enable input is pulled low, the converter is switched off
and the corresponding OUT_ and RESET_ are driven
low. If EN1 is low, all regulators are disabled.
Reset Outputs (RESET_)
The device features individual open-drain RESET_ out-
puts for each buck output that asserts when the buck
output voltage drops 6% below the regulated voltage.
RESET_ remains asserted for a fixed timeout period after
the buck output rises up to its regulated voltage. The
fixed timeout period is programmable between 0.1ms and
7.4ms (see the Selector Guide). To obtain a logic signal,
pull up RESET_ with an external resistor connected to a
positive voltage lower than 5V.
Linear Regulator (BIAS)
The device features a 5V internal linear regulator (BIAS).
Connect BIAS to PV, which acts as a supply for internal
circuitry. Also connect BIAS to PV1, which acts as a
supply for the low-side gate driver of Buck 1. Bypass
BIAS with a 2.2µF or larger ceramic capacitor as close as
possible to the device. BIAS can provide up to 100mA
(max), but is not designed to supply external loads.
Internal Oscillator
Buck 1 Clock Select (CSEL1)
The device offers a Buck 1 clock-select input. Connect
CSEL1 to GND for 2.1MHz operation. Connect CSEL1 to
BIAS to divide down the Buck 1 clock frequency by 2, 4, 5,
or 6 (see the Selector Guide). Buck 2 and Buck 3 switch
at 2.1MHz (typ) and are not controlled by CSEL1.