Rainbow-electronics MAX8707 Manual de usuario descargar pdf (Pagina 14)

MAX8707

Multiphase, Fixed-Frequency Controller for

AMD Hammer CPU Core Power Supplies

14 ______________________________________________________________________________________

Pin Description (continued)

PIN NAME FUNCTION

11 OSC

Oscillator Select Input. OSC is a 3-level logic input for selecting the per-phase switching frequency.

Connect to GND for 200kHz, connect to REF for 300kHz, or connect to V

for 600kHz per phase.

12 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.

13 TIME

Slew-Rate Adjustment Pin. Connect a resistor from TIME to GND to set the internal slew rate. A 47kΩ to

392kΩ corresponds to slew rates of 19mV/µs to 2.28mV/µs, respectively, for all suspend voltage

transitions.

where dV

TARGET

/ dt = 6.25mV/µs × 143kΩ / R

TIME

is the slew rate. For soft-start and shutdown, the

controller automatically reduces the slew rate by 1/4th. For all dynamic VID transitions, the rate at which

the VID inputs (D0–D4) are clocked sets the slew rate, as long as it is less than the dv/dt set by R

TIME

ILIM(PK)

Peak Inductor Current-Limit Threshold Adjustment (Cycle-by-Cycle Current Limit). If the voltage across the

current-sense inputs (CSP to CSN) exceeds the peak current-limit threshold, the controller immediately

terminates the respective phase’s on-time. Connect a resistor R

ILIM(PK)

from ILIM(PK)

to GND to set the

cycle-by-cycle peak current-limit threshold:

where R

is the resistance value of the current-sense element (inductors’ DCR or current-sense resistor),

TRC

is the resistance between TRC and REF, and I

PKLIMIT

is the desired peak current limit (per phase).

15 CCV

Voltage Integrator Capacitor Connection. Connect a 470pF x (4 / η

) or greater capacitor from CCV to

analog ground (GND) to set the integration time constant.

16 TRC

Transient-Voltage Preamplifier Output. Connect a resistor (R

TRC

) between TRC and REF to set the

transient droop based on the voltage-positioning requirements. TRC does not affect the DC steady-state

droop. Choose R

TRC

based on the equation:

as defined in the Design Procedure (page 33). If voltage positioning is not required, R

TRC

is determined

by the stability requirements. TRC is high impedance in shutdown.

dV dt

TRAN SUS

NEW OLD

TARGET

()

−

ILIM PK

TRC

PKLIMIT CS

()

×8

TRC CS

TRANS CS

PH DROOP AC













()

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 ... 36 37

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Rainbow-electronics MAX8707 Manual de usuario Pagina 14

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