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19-3424; Rev 0; 10/04
MAX8704 Evaluation Kit
General Description
The MAX8704 evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board that contains a MAX8704 low-voltage linear regulator for I/O supplies. The high-current, low-voltage linear regulator provides an adjustable or preset output voltage that can deliver up to 5A continuously. The EV kit requires an input voltage source of 1V to 5.5V and a low-power 5V bias supply. The MAX8704 EV kit has an output current limit, which prevents damage to the linear regulator. The EV kit also includes an adjustable power limit to protect the external MOSFET from overheating. A power-good (PGOOD) output signal is also available to indicate loss of voltage regulation. The MAX8704 is available in a 10-pin MAX(R) package.
MAX is a registered trademark of Maxim Integrated Products, Inc.
PART MAX8704EVKIT
Features
Output Voltage Range Preset to 1.2V or 1.5V (Jumper Selectable) Adjustable to as Low as 0.5V (Voltage-Dividing Resistors) Provides Up to 5A, 2.5W Power Limit 1V to 5.5V Input Voltage Range Configurable Output Current Limit Open-Drain PGOOD Output Signal Low-Profile, Surface-Mount Components Fully Assembled and Tested
Evaluates: MAX8704
Ordering Information
TEMP RANGE 0C to +70C IC PACKAGE 10 MAX
Component List
DESIGNATION C1 QTY 1 DESCRIPTION 470F 20%, 6.3V POSCAP capacitor (D4) Sanyo 6TPD470M 10F 20%, 6.3V X5R ceramic capacitor (0805) TDK C2012X5R0J106M 22F 20%, 6.3V X5R ceramic capacitors (0805) TDK C2012X5R0J226M 0.01F 10%, 50V X7R ceramic capacitor (0603) TDK C1608X7R1H103K 1F 10%, 6.3V X5R ceramic capacitor (0603) TDK C1608X5R0J105K 1000pF 10%, 50V X7R ceramic capacitor (0603) TDK C1608X7R1H102K 0.1F 10%, 50V X7R ceramic capacitor (0603) TDK C1608X7R1H104K DESIGNATION JU1 JU2 N1 QTY 1 1 1 DESCRIPTION 3-pin header 2-pin header 8.7A, 20V n-channel MOSFET (8-pin SO) International Rectifier IRF7401 115mA, 60V n-channel MOSFET (SOT23) Central Semiconductor 2N7002 Not installed, resistors (0603) 0.010 1%, 1W sense resistor (2010) IRC LRC-LRF 2010-01-R010-F 200k 1% resistor (0603) 100k 5% resistor (0603) Shunts MAX8704 PC board MAX8704EUB (10-pin MAX)
C2
1
N2 R1, R2 R3 R4 R5, R6 None None U1
1 0 1 1 2 2 1 1
C4, C5
2
C6
1
C7
1
C8
1
C9
1
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX8704 Evaluation Kit Evaluates: MAX8704
Component Suppliers
SUPPLIER Central Semiconductor International Rectifier IRC Sanyo Electronic Device TDK PHONE 631-435-1110 310-322-3331 361-992-7900 619-661-6835 847-803-6100 FAX 631-435-1824 310-726-8721 361-992-3377 619-661-1055 847-390-4405 www.irf.com www.irctt.com www.sanyodevice.com www.component.tdk.com WEBSITE www.centralsemi.com
Note: Indicate that you are using the MAX8704 EV kit when contacting these component suppliers.
Quick Start
The MAX8704 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.
9)
Connect the positive terminal of the electronic load to the VOUT pad. Connect the negative terminal of the electronic load to the GND pad.
10) Enable the electronic load's input. Repeat steps 6 and 7.
Recommended Equipment
* 5V, 100mA DC power supply (VCC) * 1V to 5.5V, 5A DC power supply (VIN) * One electronic load (e.g., HP 6060B) * One voltmeter
Detailed Description
The MAX8704 EV kit contains a low-voltage linear regulator. The regulator delivers an accurate preset or adjustable output voltage from an input voltage in the 1V to 5.5V range. The EV kit uses a separate 5V biasing power supply to power the control circuitry of the MAX8704 and drive the external n-channel power MOSFET.
Connections and Setup
1) 2) 3) Verify that no shunt is installed on jumper JU2 (EV kit ON). Connect the voltmeter to the VOUT and GND pads. Connect the positive terminal of the VCC power supply to the VCC pad. Connect the negative terminal of the VCC power supply to the GND pad. Set the VCC power supply to 5V. Connect the positive terminal of the VIN power supply to the VIN pad. Connect the negative terminal of the VIN power supply to the GND pad. Set the VIN power supply to 2V. Turn on both power supplies. Verify that the output (VOUT) is 1.5V if JU1 shunt is between pins 1 and 2, or 1.2V if JU1 shunt is between pins 2 and 3. Caution: Do not change the jumper setting on JU1 while the EV kit is powered on. Verify that PGOOD is 5V. Set the electronic load to 1A, and disable the electronic load's input.
4)
Output Voltage (VOUT) The MAX8704 EV kit features a Dual-ModeTM feedback circuit that enables the output voltage to be set by either jumper JU1, or by voltage-dividing resistors R1 and R2. Resistors R1 and R2 are not populated. In the jumper feedback mode, jumper JU1 presets the MAX8704 EV kit output voltage to either 1.2V or 1.5V (see Table 1). In the voltage-divider feedback mode, the MAX8704 EV kit's output voltage can be set by voltage-dividing resistors R1 and R2 in the following equation:
VOUT R1 VOUT = VFB x 1 + - 1 x R2 R1 = R2 VFB where R2 = 10k (typ), and VFB = 0.5V. The minimum adjustable output voltage is 0.5V (FB = CSN). The maximum adjustable output voltage is limited by the gate driver's output-voltage swing range, and the gate-threshold voltage of the selected MOSFET. Refer to the Output Voltage and Dual-Mode Feedback section in the MAX8704 IC data sheet for more information on selecting the voltage-dividing resistor values for R1 and R2.
5) 6)
7) 8)
Dual Mode is a trademark of Maxim Integrated Products, Inc. 2 _______________________________________________________________________________________
MAX8704 Evaluation Kit
Output Current Limit
The MAX8704 EV kit features an output current limit that prevents damage to the linear regulator. As configured, the output current limit is set to 5A by current-sense resistor R3. To set the output current limit to a different value, replace the surface-mount resistor R3 (2010) with a different resistor value. Refer to the Current Limit section in the MAX8704 IC data sheet for more information on setting the output current limit.
PGOOD
The MAX8704 features an open-drain power-good output (PGOOD). The MAX8704 pulls the PGOOD output pin low when the output is out of regulation, or when the EV kit is in shutdown mode. The MAX8704 EV kit includes a PGOOD PC board pad for interfacing with this signal. A pullup resistor (R5) is connected between PGOOD and VCC to provide a 5V logic-level output.
Evaluates: MAX8704
Jumper Selection
Output Voltage Selection
The MAX8704 EV kit's output voltage can be changed by the setting on jumper JU1, or by voltage-dividing resistors R1 and R2. Jumper JU1 provides the options to set the EV kit's output voltage. Table 1 lists the selectable jumper options.
External MOSFET Power Limit
The MAX8704 EV kit features a power limit to protect the external MOSFET from overheating. As configured, the external MOSFET power limit is set to 2.5W by power limiting resistor R4. To set the external MOSFET power limit to a different value, replace surface-mount resistor R4 (0603) with a different resistor value. Refer to the MOSFET Power-Limit Protection section in the MAX8704 IC data sheet for more information on setting the external MOSFET power limit.
Shutdown (SHDN and SHDN)
The MAX8704 EV kit features a shutdown mode that reduces the MAX8704 quiescent current. Jumper JU2 selects the shutdown mode for the MAX8704. Table 2 lists the selectable jumper options.
Table 1. Jumper JU1 Functions
SHUNT LOCATION 1-2 (default) 2-3 Not installed* FB PIN CONNECTED TO VCC GND Voltage-dividing resistors R1 and R2* MAX8704 EV KIT OUTPUT VOLTAGE 1.5V 1.2V
R1 VOUT = 0.5V x 1 + R2
*Refer to the Output Voltage and Dual-Mode Feedback section in the MAX8704 IC data sheet for more information on selecting the voltage-dividing resistor values for R1 and R2.
Table 2. Jumper JU2 Functions
SHUNT LOCATION Not installed (default) Not installed Not installed Installed SHDN PAD Floating Connected to external TTL source* Floating Floating SHDN PAD Floating Floating Connected to external TTL source* Floating EV KIT STATUS VOUT enabled Logic low: VOUT disabled Logic high: VOUT enabled Logic low: VOUT enabled Logic high: VOUT disabled VOUT disabled
*Note: The external TTL source can only be connected to either the SHDN pad or the SHDN pad, but not both simultaneously. _______________________________________________________________________________________ 3
MAX8704 Evaluation Kit Evaluates: MAX8704
R3 0.010 1% C4 22F C5 22F
VIN C1 470F C2 10F
5-8
N1
1-3
VOUT
GND
10 4 DRV 1 8 7 6 R2 OPEN 3 PGOOD GND 9 R1 OPEN JU1 VCC 1 2 3
GND
VCC VCC
C6 0.01F
VIN
U1 MAX8704
CSP CSN FB
2 R5 100k C7 1.0F
VCC
PGOOD
SHDN VCC 3 1 N2 2 R6 100k OPEN-DRAIN OUTPUT C8 1000pF
5
SS/EN
PLIM
4 C9 0.1F R4 200k 1%
SHDN
JU2
Figure 1. MAX8704 EV Kit Schematic
4
_______________________________________________________________________________________
MAX8704 Evaluation Kit Evaluates: MAX8704
Figure 2. MAX8704 EV Kit Component Placement Guide--Component Side
Figure 3. MAX8704 EV Kit PC Board Layout--Component Side _______________________________________________________________________________________ 5
MAX8704 Evaluation Kit Evaluates: MAX8704
Figure 4. MAX8704 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.
6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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