Pin description (continued) – Rainbow Electronics MAX8720 User Manual

Page 11

MAX8720

Dynamically Adjustable 6-Bit VID

Step-Down Controller

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Pin Description (continued)

PIN

28 QSOP

36 THIN

QFN

NAME

FUNCTION

GNDS

Ground Remote-Sense Input. For nonvoltage-positioned circuits, connect GNDS to
ground directly at the load. GNDS internally connects to the integrator that fine tunes the
output voltage. The output voltage rises by an amount of GNDS - AGND. For voltage-
positioned circuits, increase the output voltage by biasing GNDS with a resistor-divider
from REF to AGND.

PGOOD

Open-Drain Power-Good Output. PGOOD is normally high when the output is in
regulation. If V

is not within a ±15% window of the DAC setting, PGOOD is asserted

low. During DAC code transitions, PGOOD is forced high for an additional 8 clocks after
the slew-rate controller finishes the transition. PGOOD is low during shutdown. PGOOD
upper threshold is blanked whenever the MAX8720 is in pulse-skipping mode (SKIP =
GND or SUS = high).

—

GND

Analog and Power Ground. Also connects to the current-limit comparator.

16, 17

Low-Side Gate-Driver Output. DL swings from PGND to V

Supply Voltage Input for the DL Gate Driver. Connect to the system supply voltage
(+4.5V to +5.5V). Bypass V

to power ground with a 1µF or greater ceramic capacitor.

SUS

S usp end - M od e C ontr ol Inp ut. When S U S i s hi g h, the susp end - m od e V ID cod e, as
p r og r am m ed b y S 0 and S 1, i s d el i ver ed to the D AC . C onnect S U S to G N D i f the susp end -
m od e m ul ti p l exer i s not used . P GOO D up p er thr eshol d i s b l anked w hen S U S i s hi g h.

DAC Code Inputs. D0 is the LSB and D5 is the MSB for the 6-bit DAC.

SKIP

Pulse-Skipping Control Input. Connect SKIP to V

for low-noise, forced-PWM mode, or

connect SKIP to GND to enable pulse-skipping operation. PGOOD upper threshold is
blanked when SKIP = GND.

DAC Code Inputs. D0 is the LSB and D5 is the MSB for the 6-bit DAC.

BST

Boost Flying-Capacitor Connection. Connect to an external capacitor and diode as
shown in Figure 1. An optional resistor in series with BST allows the DH pullup current to
be adjusted.

Inductor Connection. Connect LX to the switched side of the inductor. LX serves as the
lower supply rail for the DH high-side gate driver. It also connects to the current-limit
comparator and the skip-mode zero-crossing comparator.

High-Side Gate-Driver Output. DH swings from LX to BST.

—

AGND

Analog Ground. Connect the backside pad to AGND.

—

14,15

PGND

Power Ground. Also connects to the current-limit comparator.

—

6, 18, 28,

30, 36

N.C.

Not internally connected.