Multiphase, Fixed-Frequency Controller forwww.DataSheet4U.com
AMD Hammer CPU Core Power Supplies
Pin Description (continued)
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 VCC for 600kHz per phase.
Ground Remote-Sense Input. Connect GNDS directly to the CPU ground-sense pin. GNDS internally
12 GNDS connects to an amplifier that adjusts the output voltage, compensating for voltage drops from the regulator
ground to the load ground.
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
| VNEW − VOLD |
dVTARGET / dt
where dVTARGET / dt = 6.25mV/µs × 143kΩ / RTIME 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 RTIME.
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 RILIM(PK) from ILIM(PK) to GND to set the
cycle-by-cycle peak current-limit threshold:
8V × RTRC
where RCS is the resistance value of the current-sense element (inductors’ DCR or current-sense resistor),
RTRC is the resistance between TRC and REF, and IPKLIMIT is the desired peak current limit (per phase).
15 CCV Voltage Integrator Capacitor Connection. Connect a 470pF x (4 / ηPH) or greater capacitor from CCV to
analog ground (GND) to set the integration time constant.
Transient-Voltage Preamplifier Output. Connect a resistor (RTRC) 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 RTRC based on the equation:
as defined in the Design Procedure (page 33). If voltage positioning is not required, RTRC is determined
by the stability requirements. TRC is high impedance in shutdown.