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19-1268; Rev 2; 12/00
MAX1636 CPU Supply Evaluation Kit
General Description
The MAX1636 CPU supply evaluation kit (EV kit) circuit is intended for converting high-voltage battery power into a low-voltage supply rail for next-generation notebook CPU cores. The output is digitally adjustable between 1.25V and 2V, in 50mV increments. The input range is +7V to +22V. It delivers up to 7A output current with greater than 87% efficiency. The MAX1636 features 1% DC output accuracy over all conditions of line, load, and temperature. The fully assembled and tested EV kit has excellent dynamic response to correct for fast load transients. This EV kit is very specific to notebook CPU core power supplies, and includes a digital-to-analog converter (DAC), op-amp buffer, and other high-performance components tailored to this demanding application. However, the MAX1636 is a general-purpose, standalone device that can be used without the DAC; see the MAX1636 data sheet for standard application circuits.
____________________________Features
o +7V to +22V Input Voltage Range o Digitally Adjustable 1.25V to 2V Output Voltage o 7A Output Current Capability o 1% DC Output Accuracy o Efficiency = 87%, VIN = 7V, VOUT = 1.7V (at IOUT = 3A) o Fast MOSFETs for Low Switching Losses o Tight PC Board Layout for Low Switching Losses o Power-Good Output o 300kHz Switching Frequency o Overvoltage and Undervoltage Protection o Surface-Mount Construction o Fully Assembled and Tested
Evaluates: MAX1636
Ordering Information
PART MAX1636CPUEVKIT TEMP. RANGE 0C to +70C IC PACKAGE 20 SSOP
Component List
DESIGNATION QTY C1, C2, C3, C4 C5, C7, C8, C9, C10 C11 C12 C13 C14, C15, C16 C14, C15, C16, C17 C18 D1 DESCRIPTION 10F, 25V ceramic capacitors Tokin C34Y5U1E106Z or United Chemicon/Marcon THCR50E1E106ZT 0.1F ceramic capacitors 1500pF ceramic capacitor 1F ceramic capacitor 4.7F, 16V tantalum capacitor Sprague 595D475X0016A2B 470F, 6.3V, 30m low-ESR tantalum capacitors Kemet T510X477M006 or 470F, 4V, 470F, 4V, 55m low-ESR tantalum low-ESR tantalum capacitors caps Sprague 594D477X0004R2T Sprague 594D477X0004R2T Open Schottky diode SGS-Thomson STPS2L25U, International Rectifier 10BQ040, or Motorola MBRS130LT3 Schottky diode Central Semiconductor CMPSH-3 N2 1 DESIGNATION QTY DESCRIPTION 2.2H power inductor Panasonic P1F2R0HL, Coiltronics UP4-2R2, or Coilcraft DO5022P-222HC N-channel MOSFET Fairchild FDS9412, International Rectifier IRF7803, or Siliconix Si9804DY N-channel MOSFET Fairchild FDS6680, International Rectifier IRF7801, or Siliconix Si4420DY 0.010, 1%, 1W resistor Dale WSL-2512-R010F 10k, 0.1% resistor Dale TNPW-1206 series 110k, 0.1% resistor Dale TNPW-1206 series 13.7k, 0.1% resistor Dale TNPW-1206 series 51, 5% resistor 100k, 5% resistors
4
L1
1
5 1 1 1
N1
1
3
R1 R2 R3 R4 R5 R6, R15
1 1 1 1 1 2
4
0 1
D2
1
________________________________________________________________ Maxim Integrated Products
1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX1636 CPU Supply Evaluation Kit Evaluates: MAX1636
Component List (continued)
DESIGNATION R7 R8-R12, R14, R15, R16 SW1 U1 U2 U3 None None JU3, JU4, JU5 QTY 1 8 1 1 1 1 1 1 3 DESCRIPTION 20, 5% resistor 1M, 5% resistors Four-position dip switch MAX1636EAP (20-pin SSOP) MAX5480BEEE (16-pin QSOP) MAX4332ESA (8-pin SO) or MAX4163ESA (alternate type with lower supply current but slightly degraded accuracy) MAX1636 PC board MAX1636 data sheet 2-pin header
Quick Start
The MAX1636 EV kit is fully assembled and tested. Follow these steps to verify board operation. Do not turn on the power supply until all connections are completed. 1) Connect a +7V to +22V supply voltage to the VIN pad. Connect ground to the GND pad. 2) Connect a voltmeter and load, if any, to the VOUT pad. 3) Turn on the power supply to the board. Verify that the output voltage is 2V (SW1 set to all zeros). 4) Set switch SW1 per Table 1 to get the desired output voltage. Input power may need to be cycled off and on for new voltage settings to take effect.
Table 1. Output Voltage Settings
Component Supplier
SUPPLIER AVX Central Semiconductor Coilcraft Dale-Vishay Fairchild International Rectifier IRC Kemet Motorola Panasonic Sanyo SGS-Thomson Siliconix Sprague Sumida Tokin Vishay/Vitramon PHONE (803) 946-0690 (516) 435-1110 (847) 639-6400 (402) 564-3131 (408) 721-2181 (310) 322-3331 (512) 992-7900 (864) 963-6300 (602) 303-5454 (201) 348-7522 (619) 661-6835 (617) 259-0300 (408) 988-8000 (603) 224-1961 (847) 956-0666 (408) 432-8020 (203) 268-6261 FAX (803) 626-3123 (516) 435-1824 (847) 639-1469 (402) 563-6418 (408) 721-1635 (310) 322-3332 (512) 992-3377 (864) 963-6521 (602) 994-6430 (201) 392-4441 (619) 661-1055 (617) 259-9442 (408) 970-3950 (603) 224-1430 (847) 956-0702 (408) 434-0375 (203) 452-5670
D3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
D2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
D1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
D0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
VOUT (V) 2.00 1.95 1.90 1.85 1.80 1.75 1.70 1.65 1.60 1.55 1.50 1.45 1.40 1.35 1.30 1.25
Note: Please indicate that you are using the MAX1636 when contacting these component suppliers.
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_______________________________________________________________________________________
MAX1636 CPU Supply Evaluation Kit
_______________Detailed Description
The MAX1636 EV kit provides a digitally adjustable output voltage between 1.25V and 2V from a +7V to +22V input supply. The output voltage is digitally adjusted by the MAX5480, a multiplying DAC, which sums a variable output current into the FB feedback node. This DAC operates in voltage-output mode and relies on the precise MAX1636 REF output to generate an accurate reference current. The DAC has buffer amplifiers on the input and output to prevent the R2R ladder in the MAX5480 from excessively loading the reference or interacting with the normal FB resistor-divider impedance. The buffered DAC output swings 0V to REF 1LSB. Refer to Table 1 for the digital-to-analog (D/A) codes. The MAX1636 IC is rated for 30V input; however, the EV kit is restricted to 22V operating range (25V absolute maximum) due to the ratings of external components and minimum duty-factor limitations.
Evaluates: MAX1636
Table 4. Jumper JU4 and JU5 Selection
SHUNT LOCATIONS JU4 Off Off On On JU5 Off On Off On OVP PIN TIED TO VCC VCC GND GND SHDN PIN TIED TO RESULT
VIN GND VIN GND
RUN mode, OVP enabled Standby mode, VL output alive RUN mode, OVP disabled Total shutdown mode
Latched Fault Protection
The MAX1636 contains a latched fault-protection circuit that disables the IC when the output is overvoltage or undervoltage (or when thermal shutdown is triggered). Once disabled, the supply won't attempt to restart until input power is cycled or until SHDN (JU5) is cycled. A fault condition can be triggered by overloading the output, overvoltaging the output (which can happen when changing the D/A code settings), or by touching sensitive compensation or feedback nodes.
Table 2. Jumper JU2 Functions
SHUNT LOCATION Off MAX1636 SKIP PIN Connected to GND Connected to VCC OPERATING MODE Idle mode, pulse-skipping operation for highest lightload efficiency Low-noise mode, fixed-frequency PWM operation.
On
Optional +5V Chip-Supply Input
An optional +5V supply input (Figure 1) can power the IC and gate drivers to improve efficiency. The idea is to power the IC from an efficient source (the +5V system supply, typically 95% efficient) instead of relying on the inefficient internal VL linear regulator. To test this feature, cut the trace at V+ and connect V+ to VL to disable the linear regulator, and connect an external +5V, 50mA supply to the optional input.
The 2-pin header JU3 selects the operating frequency. Table 3 lists the selectable jumper options. The EV kit's components are selected for 300kHz operation. Component values might need to be changed if 200kHz operation is selected (refer to the Design Procedure section in the MAX1636 data sheet). Synchronize the oscillator to an external clock signal by driving the SYNC pad with a 5V amplitude pulse train in the 240kHz to 350kHz frequency range.
Alternate Op Amp for Lower Supply Current
The MAX4332 op amp provided with this kit is very accurate but draws up to 500A supply current. For improved supply current draw with a slight (0.4%) degradation in output voltage accuracy, replace the MAX4332 with a MAX4163, which draws 25A (typ).
Table 3. Jumper JU3 Functions
SHUNT LOCATION Off On MAX1636 SYNC PIN Connected to VCC Connected to GND FREQUENCY (kHz) 300 200
The 2-pin header JU4 selects the overvoltage protection. The 2-pin header JU5 selects the shutdown mode. Table 4 lists the selectable jumper options.
_______________________________________________________________________________________
3
Evaluates: MAX1636
+5V (OPTIONAL) C8 0.1F R7 R8 1M 13 V+ VCC 4 SHDN RESET 5 8 N1 4 1 2 8 N2 10 GND 3 2 20 R14 2 JU3 8 SYNC CSL 1 JU4 5 OVP 2 R15 100k 3 4 FB C11 C18 OPEN 1500pF 1 8 VCC 0.1F 14 0.1F VDD 12 13 16 NC CS WR 3 GND VREF 2 D2 9 OUT2 D1 D0 10 11 D4 7 D3 8 6 VCC C5 C9 CC CSH 1 1M SKIP PGND 1 D1 DL 2 JU2 1 4 C15 470F 6.3V L1 2.2H R1 0.01 C14 470F 6.3V VOUT 3 C10 0.1F 67 5 BST DH 67 3 VL 12 20 14 C13 4.7F 16V D2 CMPSH-3 C7 0.1F VIN 7V TO 22V
MAX1636 CPU Supply Evaluation Kit
Figure 1. MAX1636 EV Kit Schematic
SW1A
SW1B
SW1C
1
2
3
SW1D
4
VCC
X
C1 10F 25V
C2 10F 25V
C3 10F 25V
C4 10F 25V
JU5
R6 100k
ON / OFF
PGD
9 GND
U1 MAX1636
LX
REF 7 REF R16 1M C12 1F
X
SENSE
VCC
SKIP
VCC
C16 470F 6.3V C17 470F OPEN R2 10k 0.1%
SYNC
VCC
U3B
2
U3A MAX4332
15 5 7
MAX4332
R4 13.7k 0.1% R5 51
R3 110k 0.1%
D3 1 OUT1
U2 MAX5480
D7 4 D6 5 D5 6
D2
_______________________________________________________________________________________
8 R12 1M 7 6 5 R11 1M R10 1M R9 1M VCC
D1
D0
X = CUT HERE
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MAX1636 CPU Supply Evaluation Kit Evaluates: MAX1636
1.0"
1.0"
Figure 2. MAX1636 EV Kit Component Placement Guide-- Component Side
Figure 3. MAX1636 EV Kit Component Placement Guide-- Solder Side
_______________________________________________________________________________________
5
MAX1636 CPU Supply Evaluation Kit Evaluates: MAX1636
1.0"
1.0"
Figure 4. MAX1636 EV Kit PC Board Layout--Component Side
Figure 5. MAX1636 EV Kit PC Board Layout--Two Internal GND Planes
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_______________________________________________________________________________________
MAX1636 CPU Supply Evaluation Kit Evaluates: MAX1636
1.0"
1.0"
Figure 6. MAX1636 EV Kit PC Board Layout--Three Internal GND Planes
Figure 7. MAX1636 EV Kit PC Board Layout--Solder Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ______________________7 (c) 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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