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19-4781; Rev 0; 5/00
MAX1710 Evaluation Kit
General Description
The MAX1710 evaluation kit (EV kit) demonstrates the data sheet's standard 7A notebook CPU application circuit (see MAX1710/MAX1711 data sheet). This DC-DC converter steps down high-voltage batteries and/or AC adapters, generating a precision, low-voltage CPU core VCC rail. The circuit was designed for a 7V to 24V battery range, but accommodates from 4.5V to 24V. Some parameters, such as load-transient response and maximum thermal load capability, may be degraded by going outside the 7V to 24V range. The continuous output current rating, based on worst-case MOSFET RDS(ON), heat sinking, and other thermal stress issues, is 5.5A at TA = +70C. This EV kit is a fully assembled and tested circuit board. It also allows the evaluation of the MAX1711.
Features
o High Speed, Accuracy, and Efficiency o Fast-Response QUICK-PWMTM Architecture o 7V to 24V Input Voltage Range o 1.25V to 2V Output Voltage Range o 7A Peak Load-Current Capability (5.5A Continuous) o 93% Efficient (VOUT = 2V, VBATT = 7V, ILOAD = 4A) o 300kHz Switching Frequency o No Current-Sense Resistor o Remote GND and VOUT Sensing o Power-Good Output o 24-Pin QSOP Package o Low-Profile Components o Fully Assembled and Tested
Evaluates: MAX1710/MAX1711
Ordering Information
PART MAX1710EVKIT TEMP. RANGE 0C to +70C IC PACKAGE 24 QSOP
NOTE: To evaluate the MAX1711, request a MAX1711EEG free sample with the MAX1710 EV Kit.
Component List
DESIGNATION QTY C1-C4 4 DESCRIPTION 4.7F, 25V ceramic capacitors Taiyo Yuden TMK325BJ475K D3 C1-C4 (ALTERNATE) 4 10F, 25V ceramic capacitors Tokin C34Y5U1E106Z or United Chemi Con/Marcon THCR50E1E106ZT 470F, 6.3V, 30m low-ESR tantalum capacitors Kemet T510X477M006AS 10F, 6.3V ceramic capacitor Taiyo Yuden JMK325BJ106MN or TDK C3225X5R1A106M 0.1F ceramic capacitor 0.22F ceramic capacitors 470pF ceramic capacitor 1F ceramic capacitor Not installed 2A Schottky diode SGS-Thomson STPS2L25U or Nihon EC31QS03L 100mA Schottky diode Central Semiconductor CMPSH-3 Hitachi HRB0103A N2 1 N1 1 1 DESIGNATION QTY DESCRIPTION 1A Schottky diode Motorola MBRS130LT3, Nihon EC10QS03, or International Rectifier 10BQ040 Hitachi HRF22 200mV switching diode Central Semiconductor CMPD2838 2H power inductor Panasonic ETQP6F2R0HFA, Coiltronics UP4B-2R2, or Coilcraft DO5022P-222HC N-channel MOSFET International Rectifier IRF7807, Fairchild FDS6612A, or Siliconix Si4416DY N-channel MOSFET International Rectifier IRF7805,or Fairchild FDS6670A, or NEC uPA1706, or Hitachi HAT2040R 20 5% resistor
D4
1
C5, C6, C7
3
L1
1
C8 C9 C11, C12 C14 C15 C16, C17, C18 D1
1 1 2 1 1 0 1
R1
1
QUICK-PWM is a trademark of Maxim Integrated Products.
D2
1
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800 For small orders, phone 1-800-835-8769.
MAX1710 Evaluation Kit Evaluates: MAX1710/MAX1711
Component List (continued)
DESIGNATION QTY R2, R3, R9 R4 R6 R7 R10, R12 U1 JU1, JU2 None SW1 SW2 J1 None None 3 1 0 1 1 1 2 1 1 1 1 1 1 DESCRIPTION 1M 5% resistors 100k, 5% resistor Not installed 3, 5% resistor 1k, 5% resistor MAX1710EEG (24-QSOP) 2-pin headers Shunt (JU1) DIP-8 dip switch Digi-Key CT2084-ND Momentary switch, normally open Digi-Key P8006/7S Scope-probe connector Berg Electronics 33JR135-1 MAX1710 PC board MAX1710/MAX1711 data sheet
Equipment Needed
* 7V to 24V, >20W power supply, battery, or notebook AC adapter * DC bias power supply, 5V at 100mA * Dummy load capable of sinking 7A * Digital multimeter (DMM) * 100MHz dual-trace oscilloscope
Quick Start
1) Ensure that the circuit is connected correctly to the supplies and dummy load prior to applying any power. 2) Ensure that the shunt is connected at JU1 (SHDN = VCC). 3) Turn on battery power prior to +5V bias power; otherwise, the output UVLO timer will time out and the fault latch will be set, disabling the regulator until +5V power is cycled or shutdown is toggled. 4) Observe the output with the DMM and/or oscilloscope. Look at the LX switching-node and MOSFET gate-drive signals while varying the load current. 5) Don't change the DAC code without cycling +5V bias power; otherwise, the output voltage ramp will probably bump into the over- or undervoltage protection thresholds and latch the circuit off. If this happens, just cycle power or press the RESET button. 6) Set switch SW1 per Table 1 to get the desired output voltage.
Component Suppliers
SUPPLIER Central Semiconductor Coilcraft Coiltronics Dale-Vishay Fairchild Hitachi International Rectifier IRC Kemet Motorola NEC Nihon Panasonic Sanyo SGS-Thomson Siliconix Sumida Taiyo Yuden TDK Tokin 2 PHONE 516-435-1110 708-639-6400 561-241-7876 402-564-3131 408-721-2181 888-777-0384 310-322-3331 512-992-7900 408-986-0424 602-303-5454 408-588-6000 847-843-7500 714-373-7939 619-661-6835 617-259-0300 408-988-8000 708-956-0666 408-573-4150 847-390-4373 408-432-8020 FAX 516-435-1824 708-639-1469 561-241-9339 402-563-6418 408-721-1635 650-244-7947 310-322-3332 512-992-3377 408-986-1442 602-994-6430 408-588-6130 847-843-2798 714-373-7183 619-661-1055 617-259-9442 408-970-3950 708-956-0702 408-573-4159 847-390-4428 408-434-0375
Detailed Description
This 7A buck-regulator design is optimized for a 300kHz frequency and output voltage settings around 1.6V. At lower output voltages, transient response is degraded slightly and efficiency worsens. At higher output voltages (approaching 2V), output ripple and reflected input ripple increase. The PC board layout deliberately includes long output power and ground buses in order to facilitate evaluation of the remote sense circuitry and to provide plenty of experimentation space for soldering in different types of output filter capacitors. These buses are also useful for introducing the small amounts of parasitic trace resistance necessary when using capacitors having highfrequency ESR zeros (see the All-Ceramic-Capacitor Application section in MAX1710/MAX1711 data sheet). Position the experimental ceramic capacitors at different places along the length of the buses to see the effect of different amounts of ESR.
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MAX1710 Evaluation Kit
Table 1. MAX1710/1711 Output Voltage Adjustment Settings
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 OUTPUT VOLTAGE (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
generator at a low duty cycle (10%) to minimize heat stress in the MOSFET. Vary the high-level output voltage of the pulse generator to vary the load current. To determine the load current, you might expect to insert a meter in the load path, but this method is prohibited here by the need for low resistance and inductance in the path of the dummy-load MOSFET. There are two easy alternative methods to determine how much load current a particular pulse-generator amplitude is causing. The first and best is to observe the inductor current with a calibrated AC current probe, such as a Tektronix AM503. In the buck topology, the load current is equal to the average value of the inductor current. The second method is to first put on a static dummy load and measure the battery current. Then, connect the MOSFET dummy load at 100% duty momentarily, and adjust the DC gate-drive signal amplitude until the battery current rises to the appropriate level (the MOSFET load must be well heatsinked for this to work without causing smoke and flames).
Evaluates: MAX1710/MAX1711
Efficiency Measurements
Testing the power conversion efficiency POUT/PIN fairly and accurately requires more careful instrumentation than might be expected. One common error is to use inaccurate DMMs. Another is to use only one DMM, and move it from one spot to another to measure the various input/output voltages and currents. This second error usually results in changing the exact conditions applied to the circuit due to series resistance in the ammeters. It's best to get four 3-1/2 digit or better DMMs that have been recently calibrated, and monitor VBATT, VOUT, IBATT, and ILOAD simultaneously, using separate test leads directly connected to the input and output PC board terminals. Note that it's inaccurate to test efficiency at the remote VOUT and ground terminals, as this incorporates the parasitic resistance of the PC board output and ground buses in the measurement (a significant power loss). Remember to include the power consumed by the +5V bias supply when making efficiency calculations: Efficiency = VOUT x I LOAD (VBATT x I BATT ) + (5V x I BIAS )
Setting the Output Voltage
Select the output voltage using the D0-D3 pins. The MAX1710/MAX1711 uses an internal DAC as a feedback resistor voltage-divider. The output voltage can be digitally set from 1.25V to 2V, in 50mV increments, using the D0-D3 inputs. Switch SW1 sets the desired output voltage (Table 1).
Load-Transient Measurement
One interesting experiment is to subject the output to large, fast load transients and observe the output with an oscilloscope. This necessitates careful instrumentation of the output, using the supplied scope-probe jack. Accurate measurement of output ripple and load-transient response invariably requires that ground clip leads be completely avoided and that the probe hat be removed to expose the GND shield, so the probe can be plugged directly into the jack. Otherwise, EMI and noise pickup will corrupt the waveforms. Most benchtop electronic loads intended for power-supply testing lack the ability to subject the DC-DC converter to ultra-fast load transients. Emulating the supply current i/t at the CPU VCORE pins requires at least 10A/s load transients. One easy method for generating such an abusive load transient is to solder a MOSFET, such as an MTD3055 or 12N05, directly across the scope-probe jack then drive its gate with a strong pulse
The choice of MOSFET has a large impact on efficiency performance. The International Rectifier MOSFETs used were of leading-edge performance for the 7A application at the time this kit was designed. However, the pace of MOSFET improvement is rapid, so the latest offerings should be evaluated.
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MAX1710 Evaluation Kit Evaluates: MAX1710/MAX1711
Jumper and Switch Settings
Table 2. Jumper JU1 Functions (Shutdown Mode)
SHUNT LOCATION On Off SHDN PIN Connected to VCC Connected to GND MAX1710 OUTPUT MAX1710 enabled Shutdown mode, VOUT = 0
Table 5. Jumper JU6 Functions (Fixed/Adj. Current-Limit Selection)
SHUNT LOCATION On ILIM PIN Connected to VCC CURRENT-LIMIT THRESHOLD 100mV (default)
Off
Connected to GND via external resistor R6. Refer to Adjustable the ILIM line in the Pin between 50mV Description (MAX1710/ and 200mV MAX1711 data sheet) for information on selecting R6.
Table 3. Jumper JU2 Functions (Low-Noise Mode)
SHUNT LOCATION On SKIP PIN Connected to VCC OPERATIONAL MODE Low-noise mode, forced fixedfrequency PWM operation. Normal operation, allows automatic PWM/PFM switchover for pulse skipping at light load, resulting in highest efficiency.
Table 6. Jumpers JU7/JU10 Functions (GNDS Integrator Disable Selection)
JUMPER JU7 JU10 SHUNT LOCATION On Off GND PIN Connected to VCC Connected to GND directly at the load GROUND REMOTE-SENSE Disables the GNDS integrator GNDS internally connects to the integrator that fine-tunes the ground offset voltage.
Off
Connected to GND
JU7 JU10
Off On
Table 7. Jumpers JU8/JU9 Functions (FBS and FB Integrator Disable Selection) Table 4. Jumpers JU3/JU4/JU5 Functions (Switching-Frequency Selection)
JUMPER JU3 JU4 and JU5 JU4 JU3 and JU5 JU5 JU3 and JU4 JU3, JU4, JU5 SHUNT LOCATION On Off On Off On Off Off TON PIN Connected to VCC Connected to REF Connected to GND Floating FREQUENCY (kHz) 200 400 550 300 JU8 JU9 Off On JUMPER JU8 JU9 SHUNT LOCATION On Off FBS PIN Connected to VCC Connected to VOUT directly at the load GROUND REMOTE-SENSE Disables the FBS and the main FBREF integrators FBS internally connects to the integrator that fine-tunes the DC output voltage.
IMPORTANT: Don't change the operating frequency without first re-calculating component values, because the frequency has a significant effect on the peak current-limit level, MOSFET heating, PFM/PWM switchover point, output noise, efficiency, and other critical parameters.
Table 8. Jumper JU11 Functions (Overvoltage Protection Disable)
SHUNT LOCATION On Off OVP PIN Connected to VCC Connected to GND OVERVOLTAGE PROTECTION OVP disabled Normal operation, OVP is enabled.
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MAX1710 Evaluation Kit Evaluates: MAX1710/MAX1711
Table 9. Troubleshooting Guide
SYMPTOM Circuit won't start when power is applied. POSSIBLE PROBLEM Power-supply sequencing: +5V bias supply was applied first. Output overvoltage due to shorted high-side MOSFET. Output overvoltage due to load recovery overshoot Overload condition Circuit won't start when RESET is pressed, +5V bias supply cycled. Transient overload condition SOLUTION Press the RESET button. Replace the MOSFET. Reduce the inductor value, raise the switching frequency, or add more output capacitance. Remove the excessive load or raise the ILIM threshold by changing RLIM (R6). Add more low-ESR output capacitors.
Troubleshoot the power stage. Are the DH and DL gate-drive signals present? Is the 2V VREF preBroken connection, bad MOSFET, sent? Exercising OVP mode and then SKIP or other catastrophic problem. no-fault mode can help you decipher the nature of the problem (see MAX1710/MAX1711 data sheet Pin Description). VBATT power source has poor impedance characteristic. On-time pulses are erratic or have unexpected changes in period. Noise is being injected into FB. FB is crossing the +12.5% OVP threshold or the -70% UVLO threshold due to fast DAC response. Add a bulk electrolytic bypass capacitor across the benchtop power supply, or substitute a real battery. Add an RC filter on FB (1k and 100pF suggested) at R11 and C18. This is a normal operating condition. If desired, disable the OVP fault circuit via the OVP input (JU11) or raise the OVP threshold to >2V by substituting a MAX1711 for the MAX1710.
Circuit latches off when DAC code is changed.
Add parasitic PC board trace resistance between Load-transient waveform shows excess Instability due to low-ESR ceramic the LX-FB connection and the ceramic capacitor. ringing OR LX switching waveform exhibits placed across fast OR double-pulsing (pulses separated only feedback path (FB-GND). Substitute a different capacitor type (OS-CON, tanby a 500ns min off-time). talum, aluminum electrolytic work well). Observe the gate-source voltage of N2 during the low-to-high LX node transition (this requires careful instrumentation). Is the gate voltage being pulled above 1.5V, causing N2 to turn on? Use a smaller low-side MOSFET or add a higher-value BST resistor (R7). Use a smaller high-side MOSFET or add more heatsinking.
Excessive EMI, poor efficiency at high input voltages.
Gate-drain capacitance of N2 is causing shoot-through crossconduction.
Poor efficiency at high input voltages, N1 gets hot.
N1 has excessive gate capacitance.
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5
Evaluates: MAX1710/MAX1711
MAX1710 Evaluation Kit
Figure 1. MAX1710 EV Kit Schematic
VCC R10 1k C2 10F 25V C4 10F 25V VDD V+ D2 CMPSH-3 22 24 23 C5 470F 6.3V C6 470F 6.3V C9 0.1F C7 470F 6.3V L1 2H R7 3 N1 D4 CMPD2838 3 1 C15 1F J1 SCOPE JACK 1 +5V VBIAS 7 2 SHDN VCC VDD VCC JU2 21 SKIP DH D0 LX BST R1 20 15 JU1 C11 0.22F VCC VDD C1 10F 25V C3 10F 25V R2 1M 20 8 19 D1 7 VOUT C16 OPEN C8 10F 6.3V D3 MBRS130LT3 C18 OPEN VCC OVP FBS VCC 8 TON GNDS 12 JU7 11 R12 JU8 1k VCC JU9 JU10 GNDS PGOOD VCC R4 100k R11 SHORT C17 OPEN
6
U1 MAX1710
18 D2 PGND D3 FB R8 SHORT 5 CC OVP R9 1M 16 J11 3 14 DL 6 17 5 13 N2 D1 C12 0.22F 9 REF FBS 4 FLOAT = 300kHz JU5 550kHz 6 ILIM GND 10 PGOOD
VBATT 7V TO 24V
GND
RESET SW2
SHDN
SKIP
R3 1M
D0
D1
SW1A 1
D2
SW1B 2
D3
SW1C 3
SW1D 4
C14 470pF
REF 2V
JU4 400kHz
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JU3 VCC 200kHz
JU6
R6 OPEN
MAX1710 Evaluation Kit Evaluates: MAX1710/MAX1711
1.0"
1.0"
1.0"
Figure 2. Component Placement Guide --Component Side
Figure 3. PC Board Layout--Internal GND Plane Layer 2
1.0"
1.0"
Figure 4. Component Placement Guide--Solder Side
Figure 5. PC Board Layout--Component Side 7
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MAX1710 Evaluation Kit Evaluates: MAX1710/MAX1711
1.0"
1.0"
Figure 6. PC Board Layout--Internal GND Plane Layer 3
Figure 7. 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.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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