ISL78229 Datasheet, PDF (62/71 Pages) Intersil Corporation – 2-Phase Boost Controller with Drivers

ISL78229
VOUT_UV_FAULT_LIMIT (D4h)
Definition: Set/Read the output undervoltage fault threshold. The output undervoltage fault is generated by a comparator comparing
the FB pin voltage with VOUT_UV threshold which has setting options based on percentage of the VREF_DAC reference voltage. This
command set UV threshold with 8 options ranging from 75% to 95% of the reference voltage VREF_DAC. The default is set at 80% of
VREF_DAC.
Equivalently the V_OUT undervoltage threshold is set at the same percentage of V_OUT target voltage (set by VREF_DAC) since the device
uses the same FB voltage to regulate the output voltage with the same resistor divider between V_OUT and the FB pin. For example, at
default, the V_OUT undervoltage threshold is set at 80% of V_{OUT_TARGET}. According to Equation 2 on page 26, the default V_OUT
undervoltage threshold can be calculated using Equation 32. Other threshold options can be calculated using Equation 32 with 0.8
replaced with other percentage options.
VOUT_UV
=
COMMAND

V_REFDAC



1

+
RR_{-----FF----BB----21-}
(EQ. 32)
This fault is masked before soft-start completes (t₉ as shown in Figure 67 on page 30) or when the device is disabled.
During normal operation after soft-start completes and part is enabled, when UV fault occurs, the corresponding bit in FAULT_STATUS
register is set to 1 and the SALERT pin is pulled low. But this UV fault protection response is masked by the FAULT_MASK register by
default.
For related descriptions and commands’ details, refer to “Output Undervoltage Fault” on page 35, Table 3 on page 41 and “PMBus™
Command Summary” on page 43.
Data Length in Bytes: 1
Data Format: Bit Field
Type: R/W
Protectable: Yes
Default Value: 01h, which equals to 0000_0001b, meaning 80% of VREF_DAC
Units: V (referred for the VOUT_UV threshold V_{OUT_UV} calculated by Equation 32)
COMMAND
UVP_SET (D4h)
Format
Bit Field
Bit Position
7
6
5
4
3
2
1
0
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Function
See Following Table
Default Value
0
0
0
0
0
0
0
1
BITS 7:3
(NOT USED)
Not Used
Not Used
Not Used
Not Used
Not Used
Not Used
Not Used
Not Used
BITS 2:0
000
001
010
011
100
101
110
111
PERCENTAGE OF VREF_DAC (%)
75
80
82.5
85
87.5
90
92.5
95
Submit Document Feedback ₆₂
FN8656.3
February 12, 2016