zl2106 Intersil Corporation, zl2106 Datasheet - Page 19

• Manufacturer Part Number: zl2106
• Description: 6a Digital-dc Synchronous Step-down Dc-dc Converter
• Manufacturer: Intersil Corporation

the EN pin is asserted. The internal oscillator will then
synchronize with the rising edge of the external clock.
The incoming clock signal must be in the range of 200
kHz to 1 MHz with a minimum duty cycle and must be
stable when the EN pin is asserted. The external clock
signal must also exhibit the necessary performance
requirements (see Table 3).
In the event of a loss of the external clock signal, the
output voltage may show transient over/undershoot. If
this happens, the ZL2106 will automatically switch to
its internal oscillator and switch at a frequency close to
the previous incoming frequency.
Configuration C: SYNC AUTO DETECT
When the SYNC pin is configured in auto detect mode
(CFG pin is left OPEN), the device will automatically
check for a clock signal on the SYNC pin after enable
is asserted. If a valid clock signal is present, the
ZL2106’s oscillator will then synchronize with the
rising edge of the external clock (refer to SYNC
INPUT description).
If no incoming clock signal is present, the ZL2106 will
configure the switching frequency according to the
state of the SYNC pin as listed in Table 12. In this
mode, the ZL2106 will only read the SYNC pin
connection during the start-up sequence. Changes to
the SYNC pin connection will not affect f
power (VDDS) is cycled off and on again.
Table 12. Switching Frequency Selection
If the user wishes to run the ZL2106 at a frequency not
listed in Table 12, the switching frequency can be set
using an external resistor, R
SYNC and SGND using Table 13.
SYNC Pin
Resistor
OPEN
HIGH
LOW
19
SYNC
, connected between
See Table 13
Frequency
200 kHz
400 kHz
1 MHz
SW
until the
ZL2106
Table 13. R
The switching frequency can also be set to any value
between 200 kHz and 1 MHz using the I
interface. The available frequencies are defined by f
= 8 MHz/N, where whole number N is 8 ≤ N ≤ 40. See
Application Note AN33 for details.
If a value other than f
PMBus command, the internal circuitry will select the
valid switching frequency value that is closest to the
entered value. For example, if 810 kHz is entered, the
device will select 800 kHz (N=10).
Note: The switching frequency read back using the
appropriate PMBus command will differ slightly from
the selected value in Table
hardware quantization.
When multiple Zilker Labs devices are used together,
connecting the SYNC pins together will force all
devices to synchronize with each other. The CFG pin
of one device must set its SYNC pin as an output and
the remaining devices must have their SYNC pins set
as an input or as auto detect.
Note: Precise ramp timing mode must be disabled to
use SYNC clock auto detect.
6.8 Component Selection
The ZL2106 is a synchronous buck converter with
integrated MOSFETs that uses an external inductor and
capacitors to perform the power conversion process.
The proper selection of the external components is
critical for optimized performance.
To select the appropriate external components for the
desired
requirements listed in Table 14 must be defined.
12.1 kΩ
13.3 kΩ
14.7 kΩ
16.2 kΩ
17.8 kΩ
19.6 kΩ
21.5 kΩ
10 kΩ
11 kΩ
R
SYNC
performance
SYNC
200 kHz
222 kHz
242 kHz
267 kHz
296 kHz
320 kHz
364 kHz
400 kHz
421 kHz
Resistor Values
F
SW
SW
= 8 MHz/N is entered using a
Data Sheet Revision 2/19/2009
goals,
13
. The difference is due to
23.7 kΩ
26.1 kΩ
28.7 kΩ
31.6 kΩ
34.8 kΩ
38.3 kΩ
46.4 kΩ
51.1 kΩ
R
the
SYNC
www.intersil.com
power
1000 kHz
2
471 kHz
533 kHz
571 kHz
615 kHz
727 kHz
800 kHz
889 kHz
C/SMBus
F
supply
SW
SW