MAX16818EVKIT+中文资料
General Description
The MAX16818 evaluation kit (EV kit) is a fully assem-bled and tested surface-mount printed-circuit board (PCB) designed to evaluate the MAX16818 pulse-width modulation (PWM) LED driver controller in a buck-boost configuration.
The MAX16818 EV kit operates from a DC supply volt-age of 6V to 28V. The EV kit’s output is configured to deliver at least 1A of current into an 18V series LED string. The LED brightness can be dimmed using a dig-ital PWM signal.
The EV kit provides an option to configure the MAX16818 IC’s overvoltage protection, switching fre-quency, and frequency compensation. The MAX16818EV kit also features a 180°out-of-phase clock output PCB pad.
Features
?6V to 28V Input-Voltage Range
?1A Output Current into an 18V LED String ?Pulse-Width Modulated LED Current Dimming ?Resistor-Adjustable Overvoltage Protection and Switching Frequency ?180°Out-of-Phase Clock Output ?Fully Assembled and Tested
Evaluates: MAX16818
MAX16818 Evaluation Kit
19-0842; Rev 0; 6/07
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at https://www.wendangku.net/doc/df19128963.html,.
Ordering Information
+Denotes a lead-free and RoHS-compliant EV kit.
*This limited temperature range applies to the EV kit PCB only.The MAX16818 IC temperature range is -40°C to +125°C.**EP = Exposed paddle.
E v a l u a t e s : M A X 16818
MAX16818 Evaluation Kit 2_______________________________________________________________________________________
Component List (continued)
Quick Start
Recommended Equipment Before beginning, the following equipment is needed:?6V to 28V, 5A DC power supply
? A series-connected LED string rated at 1A (maxi-mum voltage on the string should not exceed 18V)? A current probe to measure LED current
?One voltmeter
Procedure The MAX16818 EV kit is fully assembled and tested. Follow the steps below to verify board operation. Caution: Do not turn on the power supply until all connections are completed.
1)Verify that a shunt is installed across pins 2-3 of
jumper JU1.
2)Verify that no shunt is installed across jumper JU2
(EV kit on).
3)Connect the anode end of the LED string to the
LED+ pad.
4)Connect the cathode end of the LED string to the
LED- pad.
5)Clip on the current probe across the string wires to
measure the LED current.
6)Connect the positive terminal of the power supply to
the VIN pad on the EV kit. Connect the negative ter-minal of the power supply to the PGND pad next to the VIN pad.
7)Turn on the power supply and increase the voltage
to 6V or above.
8)Verify that the LED string current is approximately
1A. Adjust potentiometer R23 to obtain 1A.
9)Measure the voltage between the LED+ to LED-
PCB pads.
Detailed Description The MAX16818 EV kit is designed to evaluate the MAX16818 PWM LED driver controller in a buck-boost configuration. The EV kit PCB is designed with two layers and has 1oz copper traces. All components on the EV kit are installed on the top layer. The EV kit includes an on-board VCC regulating circuit for opera-tion with input voltage between 6V to 8V. The EV kit also includes on-board output overvoltage protection circuitry to limit the output voltage.
Input-Voltage Range
The MAX16818 EV kit can operate from a DC supply voltage of 6V to 28V and requires at least 5A. The input-voltage range is jumper selectable (see the Jumper Selection section). Transistor Q1, shunt regulator U3,
and resistors R1, R2, and R3 are used to regulate VCC
to 5V when the input voltage to the EV kit is between 6V
to 8V. If the minimum input voltage is 8V, jumper JU1
can be replaced by a shorting wire between pins 1-2. Transistor Q1, shunt regulator U3, and resistors R1, R2,
and R3 can be omitted from the EV kit, saving compo-
nents and reducing the required PCB space.
Output Current Range
The MAX16818 EV kit can deliver up to 1A into an 18V
series LED string. The maximum output current is con-figurable by sense resistor R14. The LED current can be adjusted from 400mA to 1A using potentiometer R23.
LED Brightness Dimming
The LED brightness can be dimmed using a TTL PWM
signal with a frequency range of 80H z to 5kH z. Connect the TTL dimming signal to the PWMDIM and
GND pads to control the brightness of the LEDs.
Output Overvoltage Protection
The MAX16818 EV kit features overvoltage protection circuitry to limit the voltage from LED+ to GND to 46V
when the LED string is opened. The overvoltage pro-tection circuitry consists of resistors R6–R10, transistor
Q2, and shunt regulator U4. The overvoltage protection circuitry is nonlatching.
Switching Frequency
The MAX16818 EV kit switching frequency (f SW) is con-figured to 600kH z by resistor R11. To reconfigure the
MAX16818 switching frequency from 125kH z to
1.5MHz, replace resistor R11 using the equation below:
For 120kΩ≤R11 ≤500kΩ
where f SW is the desired switching frequency in Hz.
Note: Other component values may need to be changed for proper operation. Refer to the MAX16818
IC data sheet for additional information.
Evaluates: MAX16818
MAX16818 Evaluation Kit _______________________________________________________________________________________3
E v a l u a t e s : M A X 16818
Clock Output
The MAX16818 EV kit also features a digital clock out-put that is 180°out-of-phase with respect to the high-side driver, N1. The clock output is available at the CLKOUT PCB pad.
Jumper Selection
Input-Voltage Range (VIN)
Jumper JU1 selects the input-voltage range for the MAX16818 EV kit (see Table 1 for shunt positions).
Output Enable (EN)
Jumper JU2 controls the output enable pin on the MAX16818 IC. The MAX16818 output enable pin (EN)is also connected to the overvoltage protection circuitry on the EV kit (see Table 2 for shunt positions).
MAX16818 Evaluation Kit 4_______________________________________________________________________________________
Table 2. JU2 Jumper Selection (EN)
Table 1. JU1 Jumper Selection (IN)
JU1 can be replaced by a shorting wire between pins 1-2.**Default position.
Evaluates: MAX16818
MAX16818 Evaluation Kit
_______________________________________________________________________________________
5
Figure 1. MAX16818 EV Kit Schematic
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?2007 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
E v a l u a t e s : M A X 16818
MAX16818 Evaluation Kit
Figure 2. MAX16818 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX16818 EV Kit PCB Layout—Component Side
Figure 4. MAX16818 EV Kit PCB Layout—Solder Side