Pin description (continued) – Rainbow Electronics MAX1545 User Manual

Page 15

MAX1519/MAX1545

Dual-Phase, Quick-PWM Controllers for

Programmable CPU Core Power Supplies

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PIN

NAME

FUNCTION

GNDS

Ground Remote-Sense Input. Connect GNDS directly to the CPU ground-sense pin. GNDS internally
connects to an amplifier that adjusts the output voltage, compensating for voltage drops from the
regulator ground to the load ground.

CCI

Current-Balance Compensation. Connect a 470pF capacitor between CCI and FB (see the Current-
Balance Compensation (CCI) section).

Feedback Input. FB is internally connected to both the feedback input and the output of the voltage-
positioning op amp. See the Setting Voltage Positioning section to set the voltage-positioning gain.

OAIN-

Op Amp Inverting Input and Op Amp Disable Input. When using the internal op amp for additional
voltage-positioning gain, connect to the negative terminal of the current-sense resistor through a
resistor as described in the Setting Voltage Positioning section. Connect OAIN- to V

to disable the

op amp. The logic threshold to disable the op amp is approximately V

- 1V.

OAIN+

Op Amp Noninverting Input. When using the internal op amp for additional voltage-positioning gain,
connect to the positive terminal of the current-sense resistor through a resistor as described in the
Setting Voltage Positioning section.

SKIP

Pulse-Skipping Select Input. When pulse skipping, the controller blanks the VROK upper threshold:
3.3V or V

(high) = Dual-phase forced-PWM operation,

REF = Dual-phase pulse-skipping operation,
GND = Single-phase pulse-skipping operation.

CODE

VID DAC Code Selection Output. Connect CODE to GND to select the desktop P4 code set, or
connect CODE to V

to select the mobile P4 code set (Table 4).

20–24

D4–D0

Low-Voltage VID DAC Code Inputs. The D0–D4 inputs do not have internal pullups. These 1.0V logic
inputs are designed to interface directly with the CPU. In normal mode (Table 4, SUS = GND), the
output voltage is set by the VID code indicated by the logic-level voltages on D0–D4. In suspend
mode (Table 5, SUS = REF or high), the decoded state of the four-level S0–S1 inputs sets the output
voltage.

VROK

Open-Drain Power-Good Output. After output voltage transitions, except during power-up and power-
down, if OUT is in regulation, then VROK is high impedance. The controller blanks VROK whenever
the slew-rate control is active (output voltage transitions). VROK is forced low in shutdown. A pullup
resistor on VROK causes additional finite shutdown current. During power-up, VROK includes a 3ms
(min) delay after the output reaches the regulation voltage.

BSTM

Main Boost Flying Capacitor Connection. An optional resistor in series with BSTM allows the DHM
pullup current to be adjusted.

LXM

Main Inductor Connection. LXM is the internal lower supply rail for the DHM high-side gate driver.

DHM

Main High-Side Gate-Driver Output. Swings LXM to BSTM.

DLM

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

. DLM is forced high after the

MAX1519/MAX1545 power down.

Supply Voltage Input for the DLM and DLS Gate Drivers. Connect to the system supply voltage (4.5V
to 5.5V). Bypass V

to PGND with a 2.2µF or greater ceramic capacitor as close to the IC as

possible.

Pin Description (continued)