ZL2105ALNF Intersil, ZL2105ALNF Datasheet - Page 19

• Manufacturer Part Number: ZL2105ALNF
• Description: IC DGTL DC-DC CTRLR 3A 36QFN
• Manufacturer: Intersil
• Type: Step-Down (Buck), PWM - Voltage Moder

Specifications of ZL2105ALNF

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 V ~ 5.5 V
• Current - Output: 3A
• Frequency - Switching: 200kHz ~ 2MHz
• Voltage - Input: 4.5 V ~ 14 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: *
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 14. R
The switching frequency can also be set to any value
between 200 kHz and 2 MHz using the I
interface. The available frequencies are bounded by f
= 8 MHz/N, where 4≤N≤40. See Application Note
AN2013 for details.
If 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.
Note: The switching frequency read back using the
appropriate PMBus command will differ slightly from
the selected value in Table 14. The difference is due to
hardware quantization.
5.9 Component Selection
The ZL2105 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. For more detailed
guidelines regarding component selection, refer to
Application Note AN2011.
To select the appropriate external components for the
desired
requirements listed in Table 15 must be known.
200 kHz
222 kHz
242 kHz
267 kHz
296 kHz
320 kHz
364 kHz
400 kHz
421 kHz
471 kHz
533 kHz
F
SW
performance
SYNC
12.1 k
13.3 k
14.7 k
16.2 k
17.8 k
19.6 k
21.5 k
23.7 k
26.1 k
10 k
11 k
R
Resistor Values
SYNC
19
goals,
1000 kHz
1143 kHz
1333 kHz
1600 kHz
2000 kHz
571 kHz
615 kHz
667 kHz
727 kHz
889 kHz
F
the
SW
power
28.7 k
31.6 k
34.8 k
38.3 k
46.4 k
51.1 k
56.2 k
68.1 k
82.5 k
2
100 k
C/SMBus
R
SYN
supply
SW
ZL2105
Table 15. Power Supply Requirements
5.9.1 Design Goal Trade-offs
The design of the buck power stage requires several
compromises among size, efficiency, and cost. The
inductor core loss increases with frequency, so there is
a trade-off between a small output filter made possible
by a higher switching frequency and getting better
power supply efficiency. Size can be decreased by
increasing the switching frequency at the expense of
efficiency. Cost can be minimized by using through-
hole
components are physically large.
To start the design, select a frequency based on Table
16. This frequency is a starting point and may be
adjusted as the design progresses.
Table 16. Circuit Design Considerations
5.9.2 Inductor Selection
The output inductor selection process must include
several trade-offs. A high inductance value will result
in a low ripple current (I
capacitance and produce a low output ripple voltage,
but may also compromise output transient load
performance. Therefore, a balance must be struck
between output ripple and optimal load transient
Input voltage (V
Output voltage (V
Output current (I
Output voltage ripple
(V
Output load step (I
Output load step rate
Output deviation due to load
step
Maximum PCB temp.
Desired efficiency
Other considerations
orip
200–400 kHz
400–800 kHz
Frequency
)
800 kHz –
Range
2 MHz
inductors
Parameter
IN
OUT
)
OUT
ostep
)
)
)
and
Efficiency
Moderate
Highest
opp
capacitors;
Lower
), which will reduce output
< 3% of V
4.5–14.0 V
0.6–5.5 V
0 to 3 A
Range
120°C
< Io
—
—
—
—
OUT
however
March 30, 2011
Circuit Size
Smallest
Smaller
Larger
Optimize for
1% of V
small size
FN6851.2
Example
50% of I
10 A/µS
50 mV
Value
1.2 V
85°C
12 V
85%
2 A
OUT
these
o