zl2103 Intersil Corporation, zl2103 Datasheet - Page 20

• Manufacturer Part Number: zl2103
• Description: 3a Digital-dc Synchronous Step-down Dc/dc Converter
• Manufacturer: Intersil Corporation

In the ZL2103, the compensation zeros are set by configuring the
FC pin or via the I
calculated the required settings. This method eliminates the
inaccuracies due to the component tolerances associated with
using external resistors and capacitors required with traditional
analog controllers.
The loop compensation coefficients can also be set via the
I
for further details. Also refer to Application Note AN2035 for
further technical details on setting loop compensation.
Driver Dead-time Control
The ZL2103 utilizes a predetermined fixed dead-time applied
between the gate drive signals for the top and bottom MOSFETs.
In a synchronous buck converter, the MOSFET drive circuitry must
be operated such that the top and bottom MOSFETs are never in
2
C/SMBus interface. Please refer to Application Note
TABLE 12. RESISTOR SETTING FOR LOOP COMPENSATION
G
24
27
27
27
27
27
27
27
27
27
27
30
30
30
30
30
30
30
30
30
30
33
33
33
33
33
33
33
33
33
33
(dB)
0.150
0.150
0.150
0.150
0.300
0.300
0.300
0.300
0.600
0.600
0.600
0.150
0.150
0.150
0.300
0.300
0.300
0.300
0.600
0.600
0.600
0.150
0.150
0.150
0.300
0.300
0.300
0.300
0.600
0.600
0.600
2
C/SMBus interface once the user has
Q
20
115.000
115.000
115.000
115.000
115.000
115.000
115.000
69.147
41.577
69.147
41.577
25.000
69.147
41.577
25.000
69.147
41.577
69.147
41.577
25.000
69.147
41.577
25.000
69.147
41.577
69.147
41.577
25.000
69.147
41.577
25.000
fsw/fn
High or 12.1
Open or 11
Low or 10
100.0
110.0
121.0
133.0
162.0
178.0
147.0
13.3
14.7
16.2
17.8
19.6
21.5
23.7
26.1
28.7
31.6
34.8
38.3
42.2
46.4
51.1
56.2
61.9
68.1
75.0
82.5
90.9
(k)
FC
AN2033
ZL2103
the conducting state at the same time. This is because
potentially damaging currents flow in the circuit if both MOSFETs
are on simultaneously for periods of time exceeding a few
nanoseconds. Conversely, long periods of time in which both
MOSFETs are off reduces overall circuit efficiency by allowing
current to flow in their parasitic body diodes.
Therefore, it is advantageous to minimize the dead-time to
provide peak optimal efficiency without compromising system
reliability. The ZL2103 has optimized the dead-time for the
integrated MOSFETs to maximizing efficiency.
Power Management Functional
Description
Input Undervoltage Lockout
The input undervoltage lockout (UVLO) prevents the ZL2103 from
operating when the input falls below a preset threshold,
indicating the input supply is out of its specified range. The UVLO
threshold (V
pin according to Table 6.
The UVLO voltage can also be set to any value between 2.85V
and 16V via the I
Once an input undervoltage fault condition occurs, the device
can respond in a number of ways as follows:
The default response from a UVLO fault is an immediate shutdown
of the device. Please refer to Application Note AN2033 for details on
how to configure the UVLO threshold or to select specific UVLO fault
response options via the I
Output Overvoltage Protection
The ZL2103 offers an internal output overvoltage protection
circuit that can be used to protect sensitive load circuitry from
being subjected to a voltage higher than its prescribed limits. A
hardware comparator is used to compare the actual output
voltage (seen at the VSEN pin) to a threshold set to 15% higher
than the target output voltage (the default setting). If the VSEN
voltage exceeds this threshold, the PG pin will de-assert and the
device can then respond in a number of ways as follows:
The default response from an overvoltage fault is to immediately
shut down. For continuous overvoltage protection when operating
from an external clock, the only allowed response is an
immediate shutdown. Please refer to Application Note
1. Continue operating without interruption.
2. Continue operating for a given delay period, followed by
3. Initiate an immediate shutdown until the fault has been
1. Initiate an immediate shutdown until the fault has been
2. Turn off the high-side MOSFET and turn on the low-side
shutdown if the fault still exists. The device will remain in
shutdown until instructed to restart.
cleared. The user can select a specific number of retry
attempts.
cleared. The user can select a specific number of retry
attempts.
MOSFET. The low-side MOSFET remains on until the device
attempts a restart.
UVLO
) can be set to either 4.5V or 10.8V using the SS
2
C/SMBus interface.
2
C/SMBus interface.
AN2033
May 3, 2011
FN6966.5