EN6337QI3 ENPIRION [Enpirion, Inc.], EN6337QI3 Datasheet - Page 10

• Manufacturer Part Number: EN6337QI3
• Description: 3A Voltage Mode Synchronous Buck PWM DC-DC Converter with Integrated Inductor
• Manufacturer: ENPIRION [Enpirion, Inc.]

Additional Features:
• The switching frequency can be phase-
• Soft-start circuit allowing controlled startup
• Power good circuit indicating the output
• To maintain high efficiency at low output
Enable Operation
The ENABLE pin provides a means to enable
normal operation or to shut down the device.
When the ENABLE pin is asserted (high) the
device will undergo a normal soft start. A logic
low on this pin will power the device down in a
controlled manner. From the moment ENABLE
goes low, there is a fixed lock out time before
the output will respond to the ENABLE pin re-
asserted
even very short logic low pulses on the
ENABLE pin. See the Electrical Characteristics
Table for technical specifications for this pin.
LLM/SYNC Pin
This is a dual function pin providing LLM
Enable and External Clock Synchronization. At
static Logic HIGH, device will allow automatic
engagement of light load mode. At static logic
LOW, the device is forced into PWM only. A
clocked input to this pin will synchronize the
internal switching frequency – LLM mode is not
available if this input is clocked. If this pin is
left floating, it will pull to a static logic high,
enabling LLM.
Frequency Synchronization
The
converter can be phase-locked to an external
clock
frequencies out of band. To avail this feature,
the clock source should be connected to the
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05800
locked to an external clock to eliminate or
move beat frequency tones out of band.
when the converter is initially powered up.
The soft start time is programmable with an
appropriate choice of soft start capacitor.
voltage is greater than 90% of programmed
value as long as feedback loop is closed.
current, the device incorporates automatic
light load mode operation.
switching
source
(high).
This lock out is activated for
to
frequency
move
of
unwanted
the
DC/DC
beat
6/17/2011
10
LLM/SYNC pin. An activity detector recognizes
the presence of an external clock signal and
automatically phase-locks the internal oscillator
to this external clock. Phase-lock will occur as
long as the clock frequency is in the range
specified in the Electrical Characteristics Table.
For proper operation of the synchronization
circuit, the high-level amplitude of the SYNC
signal should not be above 2.5V. Please note
LLM is not available when synchronizing to an
external frequency.
Spread Spectrum Mode
The external clock frequency may be swept
between the limits specified in the Electrical
Characteristics Table at repetition rates of up
to 10 kHz in order to reduce EMI frequency
components.
Soft-Start Operation
During Soft-start, the output voltage is ramped
up gradually upon start-up. The output rise
time is controlled by the choice of soft-start
capacitor, which is placed between the SS pin
(30) and the AGND pin (32).
During start-up of the converter, the reference
voltage to the error amplifier is linearly
increased to its final level by an internal current
source of approximately 10uA. Typical soft-
start rise time is ~1.2mS with SS capacitor
value of 15nF. The rise time is measured from
when V
crosses its logic high threshold to when V
reaches its programmed value. Please note
LLM function is disabled during the soft-start
ramp-up time.
POK Operation
The POK signal is an open drain signal
(requires a pull up resistor to V
voltage) from the converter indicating the
output voltage is within the specified range.
The POK signal will be logic high (V
the
programmed V
below this threshold, the POK signal will be
logic low.
Rise Time: T
output
IN
> V
UVLOR
voltage
OUT
. If the output voltage goes
R
≈ (C
and ENABLE pin voltage
is
SS
* 80kΩ) ± 25%
www.enpirion.com
above
IN
EN6337QI
or similar
90%
IN
) when
Rev: B
OUT
of