ISL78229 Datasheet, PDF (49/71 Pages) Intersil Corporation – 2-Phase Boost Controller with Drivers

ISL78229
VOUT_TRANSITION_RATE (27h)
Definition: When the ISL78229 receives VOUT_COMMAND that causes the VREF_DAC and eventually output voltage to change, this
command sets the rate in mV/ms at which the VREF_DAC changes, and correspondingly sets the rate at which the output voltage
changes. This commanded rate of change does not apply when the unit is commanded to turn on or to turn off.
The VOUT_TRANSITION_RATE command has two data bytes formatted in bit field as shown in the table below. Bits [15:3] are not used
and Bits [2:0] defines the transition rate of the VREF_DAC with default value of 0004h meaning 200mV/ms for VREF_DAC transition
rate (per table below), and 8 options ranging from 12.5mV/ms to 1600mV/ms.
According to Equation 2 on page 26, Equation 24 below can be used to convert the V_REFDAC transition rate (V_REFDACTR) to the V_OUT
transition rate (V_OUTTR), where R_FB2 and R_FB1 are resistor dividers from V_OUT to FB as shown in Figure 3 on page 7.
V_OUTTR
=
V_REF
D
A
C
T
R




1
+
RR_{-----FF----BB----21-}
(EQ. 24)
Data Length in Bytes: 2
Data Format: Bit Field
Type: R/W
Protectable: Yes
Default Value: 0004h, which equals to 0000_0100b, meaning 200mV/ms as for transition rate of VREF_DAC
Units: mV/ms (referred for V_REFDAC transition rate)
Equation: Use Equation 24 to convert the V_REFDAC transition rate (V_REFDACTR) to the V_OUT transition rate (V_OUTTR).
Range: 12.5mV/ms to 1600mV/ms for V_REFDAC transition rate
Example: VOUT_TRANSITION_RATE = 0003h = 0000_0000_0000_0011b sets the V_REFDAC transition rate to be 100mV/ms. Using
Equation 24 with R_FB1 = 4.53kΩ and R_FB2 = 97.6kΩ (Figure 4 on page 8), the V_OUT transition rate (V_OUTTR) is calculated to be
2.25V/ms.
COMMAND
Format
Bit Position
Access
Function
Default Value
VOUT_TRANSITION_RATE (27h)
Bit Field
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
See Following Table
0000000000000100
BITS 15:3
(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
TRANSITION RATE OF VREF_DAC (mV/ms)
12.5
25
50
100
200
400
800
1600
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FN8656.3
February 12, 2016