Datasheet

MAX16993 Step-Down Controller with
Dual 2.1MHz Step-Down DC-DC Converters
www.maximintegrated.com
Maxim Integrated │ 13
Spread-Spectrum Enable (SSEN)
The device features a spread-spectrum enable (SSEN)
input that can quickly enable spread-spectrum operation
to reduce radiated emissions. Connect SSEN to BIAS to
enable the spread-spectrum oscillator. Connect SSEN
to GND for standard oscillator operation. When spread
spectrum is enabled, the internal oscillator frequency
is varied between f
SW
and (f
SW
+ 6%). The change in
frequency has a sawtooth shape and a frequency of 4kHz
(see Figure 1). This function does not apply to externally
applied oscillation frequency. See the Selector Guide for
available options.
Synchronization (SYNC)
SYNC is factory-programmable I/O. See the Selector
Guide for available options. When SYNC is configured as
an input, a logic-high on SYNC enables fixed-frequency,
forced-PWM mode. Apply an external clock on the SYNC
input to synchronize the internal oscillator to an external
clock. The SYNC input accepts signal frequencies in the
rangeof1.7MHz<f
SYNC
<2.4MHz.Theexternalclock
should have a duty cycle of 50%. A logic-low at the SYNC
input enables the device to enter a low-power skip mode
under light-load conditions.
Common Protection Features
Undervoltage Lockout
The device offers an undervoltage-lockout feature.
Undervoltage detection is performed on the PV input. If
V
SUP
decreases to the point where Buck 1 is in drop-
out, PV begins to decrease. If PV falls below the UVLO
threshold (2.7V, typ), all three converters switch off and
the RESET_ outputs assert low. Once the device has
been switched off, V
SUP
must exceed the V
SUP,STARTUP
threshold before Buck 1 turns back on.
Output Overvoltage Protection
The device features overvoltage protection on the buck
converter outputs. If the FB1 input exceeds the output
overvoltage threshold, a discharge current is switched on
at OUT1 and RESET1 asserts low.
Figure 1. Effect of Spread Spectrum on Internal Oscillator
f
SW + 6%
f
SW
tt + 250µs t + 500µs t + 750µs
INTERNAL OSCILLATOR
FREQUENCY
TIME