
M
Triple-Output Buck Controller with
Tracking/Sequencing
______________________________________________________________________________________
11
Pin Description (continued)
PIN
NAME
FUNCTION
16
FB1
Controller 1 Feedback Regulation Point. Connect to the center tap of a resistive divider from the converter
output to SGND to set the output voltage. The FB1 voltage regulates to V
FB
(0.6V).
17
PGOOD1
Controller 1 Power-Good Output. Open-drain PGOOD1 output goes high impedance (releases) when FB1 is
above 0.925 x V
FB
= 0.555V.
18
PGND2
Controller 2 Power Ground Connection. Connect the input filter capacitor’s negative terminal, the source of
the synchronous MOSFET, and the output filter capacitor’s return to PGND2. Connect externally to SGND at
a single point near the input capacitor return terminal.
19
DL2
Controller 2 Low-Side Gate Driver Output. DL2 is the gate driver output for the synchronous MOSFET.
20
DREG2
Controller 2 Low-Side Gate Driver Supply. Connect externally to REG and the anode of the boost diode.
Connect at minimum, a 0.1μF ceramic capacitor from DREG2 to PGND2.
21
LX2
Controller 2 High-Side MOSFET Source Connection/Synchronous MOSFET Drain Connection. Connect the
inductor and the negative side of the boost capacitor to LX2.
22
DH2
Controller 2 High-Side Gate Driver Output. DH2 drives the gate of the high-side MOSFET.
23
BST2
Controller 2 High-Side Gate Driver Supply. Connect BST2 to the cathode of the boost diode and to the
positive terminal of the boost capacitor.
24
CSN2
Controller 2 Negative Current-Sense Input. Connect CSN2 to the synchronous MOSFET drain (connected to
LX2). When using a current-sense resistor, connect CSN2 to the junction of the low-side MOSFET’s source
and the current-sense resistor. See Figure 11.
25
CSP2
Controller 2 Positive Current-Sense Input. Connect CSP2 to the synchronous MOSFET source (connected to
PGND2). When using a current-sense resistor, connect CSP2 to the PGND2 end of the current-sense
resistor.
26
ILIM2
Controller 2 Valley Current-Limit Set Output. Connect a 25k
to 150k
resistor, R
ILIM2
, from ILIM2 to SGND
to program the valley current-limit threshold from 50mV to 300mV. ILIM2 sources 20μA out to R
ILIM2
. The
resulting voltage divided by 10 is the valley current-limit threshold. When using a precision current-sense
resistor, connect a resistive divider from REG to ILIM2 to SGND to set the valley current limit. See Figure 11.
27
COMP2
Controller 2 Error Transconductance Amplifier Output. Connect COMP2 to the compensation feedback
network.
28
EN/TRACK2
Controller 2 Enable/Tracking Input. See Figure 2.
When sequencing, EN/TRACK2 must be above 1.24V for the PWM controller 2 to start.
Coincident tracking—connect the same resistive divider used for FB2, from Output 1 to EN/TRACK2 to
SGND.
Ratiometric tracking—connect EN/TRACK2 to analog ground.
29
FB2
Controller 2 Feedback Regulation Point. Connect to the center tap of a resistive divider from the converter
output to SGND to set the output voltage. The FB2 voltage regulates to V
FB
(0.6V).
30
PGOOD2
Controller 2 Power-Good Output. Open-drain PGOOD2 output goes high impedance (releases) when FB2 is
above 0.925 x V
FB
= 0.555V.
31
PGOOD3
Controller 3 Power-Good Output. Open-drain PGOOD3 output goes high impedance (releases) when FB3 is
above 0.925 x V
FB
= 0.555V.
32
FB3
Controller 3 Feedback Regulation Point. Connect to the center tap of a resistive divider from the converter
output to SGND to set the output voltage. The FB3 voltage regulates to V
FB
(0.6V).