Dual, 3A, 2MHz Step-Down Regulator
For ratiometric tracking applications, connect REFIN to
the center of a voltage-divider from the output of regula-
tor 2 to GND (see Figure 3b). In this application, the EN_
inputs are connected to each other and driven as a sin-
gle enable input. Regulator 2 starts up with a normal soft-
start (CSS2 sets the time), and regulator 1 output
ratiometrically tracks the regulator 2 output voltage. The
voltage-divider resistors set the VOUT1/VOUT2 ratio (see
the Setting the Output Voltage section). In Figure 3b,
VOUT1 regulates to half of VOUT2. Note that a capaci-
tance of 1000pF should be connected to SS1 for stability.
Figure 3c shows the output sequencing application
using an external reference.
Sequencing is achieved by connecting EN2 to
PWRGD1. In this mode, regulator 2 starts once regulator
1 reaches regulation.
EN
PWRGD1 EN1
EN
10kΩ
OUT2
VDD
EN2
OUT1
10kΩ
PWRGD2
PWRGD2 SS2
PWRGD1
SS1
REFIN
OUT2
10kΩ
10kΩ
Figure 3b. Startup and Sequencing Options—Ratiometric Tracking Startup and Shutdown Waveforms VOUT1 Track VOUT2
EN1
OUT1
10kΩ
PWRGD1
10kΩ
OUT2
PWRGD2
PWRGD1 EN1
EN1
VDD
EN2
SS2
PWRGD2
SS1
REFIN
REFIN
Figure 3c. Startup and Sequencing Options—Sequencing Startup and Shutdown Waveforms with External Reference
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