アプリケーションノート 3499

Compact-Footprint, 60A, Two-Phase Power Supply for AMD K8 Motherboards


要約: This application note describes a compact-footprint, low-cost, 60A, two-phase solution for desktop motherboard applications using AMD K8 CPUs. Test data, schematics, and bill of materials are included. The regulator operates from a 12V input and delivers a peak efficiency of 90% with a four-layer, 1oz. copper PC board typically employed in desktop designs. It features a 5in x 1.3in regulator area footprint, and uses low-cost components. Adequate airflow is necessary to ensure that the board/component temperature rise is within acceptable limits for the required operating ambient-temperature range.

The power supply is implemented using the MAX1937 Quick-PWM™ controller. The Quick-PWM architecture regulates the output voltage by driving the output inductor with a constant on-time pulse whenever the output-voltage ripple waveform falls below a reference voltage (Figure 1). The next pulse is applied to the inductor after a fixed minimum off-time, if the output voltage has fallen below the reference. Unlike fixed-frequency controllers that have to wait for the next clock pulse to service load transients, the Quick-PWM control architecture responds after the minimum off-time (350ns for the MAX1937) has elapsed. This ensures fast response under load-transient conditions. The steady-state switching frequency can still be low (180kHz in this design) to maximize efficiency.

Load-transient response (Figure 2) and efficiency data (Figure 3) are shown, along with a bill of materials (Table 1) and schematics of a two-phase power supply for AMD K8 motherboards (Figures 4a and 4b).

Figure 1. Quick-PWM operation.
Figure 1. Quick-PWM operation.

Figure 2. Load-transient response.
Figure 2. Load-transient response.

Figure 3. Efficiency (VIN = 12V, VOUT = 1.5V).
Figure 3. Efficiency (VIN = 12V, VOUT = 1.5V).

Table 1. Bill of Materials
DESIGNATION QTY DESCRIPTION
C1, C2, C20, C64 4 1500µF, 16V capacitors
Rubycon 16VMBZ1500
C3, C9 2 10µF, 16V capacitors (1210)
Taiyo Yuden CE EMK325 BJ106MN-T
C4, C6 2 0.22µF, 10V X7R capacitors (0603)
Taiyo Yuden CE LMK107 BJ334KA-T
C5, C7 2 1000pF, 6.3V X7R capacitors (0603)
Murata GRM39X7R102K
C8 1 2.2µF, 6.3V capacitor (0603)
Taiyo Yuden CE JMK107 BJ105MA-T
C10 1 820pF, C0G capacitor (0603)
Murata GRM39C0G821J050
C11, C14 1 0.22µF, 10V X7R capacitors (0603)
Taiyo Yuden CE LMK107 BJ224KA-T
C12, C13 2 2200pF, 6.3V X7R capacitors (0603)
Murata GRM39X7R222K
C15 1 47pF, 50V C0G capacitors (0603)
Murata GRM39C0G470J050AD
C16 1 Not used
C17 1 0.47µF, 10V X5R capacitor (0603)
Taiyo Yuden CE LMK107 BJ474KA-T
C18, C19 2 0.0022µF, 50V capacitors (0805)
Murata GRM39X7R222K50
C21 1 0.1µF, 25V X7R capacitor (0603)
Murata GRM188R71E104KA01B
C22-C27 6 3300µF, 6.3V capacitors
Rubycon 6.3VMBZ3300,
12ΩWMAX ESR
C28-C33, C34-C39 12 10µF capacitors (1206)
Taiyo Yuden CE JMK316 BJ106ML-T
C40-C47, C48-C61 22 2.2µF capacitors (0603)
Taiyo Yuden JMK107BJ225MA
C62-C63, C67-C70 6 22µF X5R capacitors (1206)
Taiyo Yuden JMK316BJ226ML
R1 1 10Ω ±5% resistor (0603)
R2, R5 2 3.3Ω ±5% resistors (0603)
R3 1 10kΩ ±5% resistor (0603)
R4, R7, R8, R9 4 200Ω ±5% resistors (0603)
R6 2 20kΩ ±1% resistor (0603)
R16, R17 2 68.1kΩ ±5% resistors (0603)
R8, R9 2 200Ω ±5% resistors (0603)
R10 1 100kΩ ±1% resistor (0603)
R11 1 2kΩ ±5% resistor (0603)
R12 1 120kΩ ±1% resistor (0603)
R13 1 80.6kΩ ±1% resistor (0603)
R14, R15 2 200kΩ ±1% resistors (0603)
R18, R19 2 3.3Ω ±5% resistors (1206)
R20 1 Open (0603)
R21 1 390Ω ±1% resistor (0603)
R22 1 1.5kΩ ±1% resistor (0603)
R29 1 2.2Ω ±5% resistor (0603)
L1, L2 1 1.2µH, 30A toroidal inductors
BI Technologies HM00-3583
L3 1 0.33µH, 10A toroidal inductor
BI Technologies HM00-3661
D1 1 Dual Schottky diodes (SOT23)
Central CMSSH-3A
D2, D3 2 Diodes (SOT23)
Central Semiconductor CMPD2836
J1-J6, J9 7 2-pin headers
Q3, Q4, Q7, Q8 4 N-channel MOSFETs (D2-Pak)
International Rectifier IRLR7833S
Q1, Q2, Q5, Q6 4 N-channel MOSFETs (D-Pak),
International Rectifier IRLR7821
Q9, Q10 2 N-channel MOSFETs (SOT23)
Vishay 2N7002
U1 1 Maxim MAX1937EEI controller (QSOP)
U2 1 National LM317 regulator (D-Pak)
J7 1 4-pin ATX Molex connector
J8 1 PGA socket 754
Foxconn PZ75403-2948-01
PC board 1 Maxim MAX1937 K8 evaluation kit,
8/03, compact footprint

Figure 4a. 60A, Two-Phase Power Supply for AMD K8 Motherboards (VIN = 12V, VOUT = 1.5V at 60A)
For Larger Image

Figure 4a. 60A, Two-Phase Power Supply for AMD K8 Motherboards (VIN = 12V, VOUT = 1.5V at 60A)

Figure 4b. 60A, Two-phase power supply for AMD K8 motherboards.
Figure 4b. 60A, Two-phase power supply for AMD K8 motherboards.

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APP 3499:
アプリケーションノート 3499,AN3499, AN 3499, APP3499, Appnote3499, Appnote 3499