general description the max9820 evaluation kit (ev kit) demonstrates the max9820 stereo headphone amplifier with external gain and directdrive outputs for portable applications. maxim? directdrive technology eliminates the need for bulky dc-blocking capacitors at the output of the amplifier. the max9820 ev kit is configured for a -1v/v gain and is designed to operate from a 2.7v to 5.5v dc power supply. the ev kit is capable of delivering up to 95mw into a 32 load and achieves 0.005% thd+n. features ? no dc-blocking output capacitors required ? 2.7v to 5.5v operation ? adjustable -1v/v gain ? 95mw into a 32 load ? 0.005% thd+n ? lead(pb)-free and rohs compliant ? fully assembled and tested evaluates: max9820 max9820 evaluation kit ________________________________________________________________ maxim integrated products 1 19-4948; rev 0; 9/09 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. ordering information part type MAX9820EVKIT+ ev kit + denotes lead(pb)-free and rohs compliant. component list designation qty description c1, c2 2 1? ?0%, 50v x7r ceramic capacitors (0805) murata grm21br71h105k c3 1 10? ?0%, 10v x5r ceramic capacitor (0805) murata grm21br61a106k c4 1 0.1? ?0%, 16v x7r ceramic capacitor (0603) murata grm188r71c104k c5, c6 2 1? ?0%, 10v x5r ceramic capacitors (0603) murata grm188r61a105k c1p, vss 0 n ot i nstal l ed , m i ni atur e p c b test p oi nts hpout 1 stereo headphone jack (3.5mm) designation qty description ju1 1 2-pin header outl 1 white miniature pcb test point outr 1 red miniature pcb test point pgnd 1 black miniature pcb test point r1?4 4 40.2k 1% resistors (0603) r5 1 10k 5% resistor (0603) u1 1 external gain headphone amplifier (10 tdfn-ep*) maxim max9820etb+ (top mark: aau) 1 shunt (ju1) 1 pcb: max9820 evaluation kit+ directdrive is a registered trademark of maxim integrated products, inc. * ep = exposed pad. supplier phone website murata electronics north america, inc. 770-436-1300 www.murata-northamerica.com component supplier note: indicate that you are using the max9820 when contacting this component supplier.
evaluates: max9820 quick start required equipment 2.7v to 5.5v, 500ma power supply one set of stereo headphones audio signal source procedure the max9820 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 on jumper ju1 (ic disabled). 2) set the power-supply output to 5v. 3) disable the power-supply output. 4) connect the power-supply ground to the pgnd pcb pad and the power-supply positive output to the vdd pcb pad. 5) verify that the audio source output is disabled. 6) connect the audio source ground, left signal, and right signal to the gnd, vinl, and vinr pcb pads, respectively. 7) plug the headphone into the hpout headphone jack. 8) enable the power-supply output. 9) enable the audio source. 10) remove the shunt from jumper ju1 (ic enabled). 11) verify that the headphones are playing the audio source signal. detailed description of hardware the max9820 ev kit features the max9820 stereo headphone amplifier, in a 10-pin tdfn package with an exposed pad, for portable applications. the max9820 ic features adjustable gain and directdrive outputs. directdrive generates an internal negative supply (-vdd) from the external positive supply (vdd), thus biasing the output signal at 0v dc. zero-voltage bias- ing eliminates the need for bulky dc-blocking capaci- tors at the output of the amplifier. the max9820 oper- ates from a 2.7v to 5.5v, 500ma power supply. the ev kit? gain for each channel is set to -1v/v. the left- and right-channel gain can be adjusted by modify- ing the ratio of the corresponding gain-setting resistors (r1?4). r1 and r4 set the left-channel gain, while r2 and r3 set the right-channel gain. the gain for either channel can be adjusted to a minimum of -1v/v. the ic delivers up to 95mw into a 32 load, while achieving 0.005% thd+n. test points outr, outl, and pgnd are provided to easily measure the output signals. shutdown ( shdn ) jumper ju1 controls the shutdown pin ( shdn ) of the max9820, which enables and disables the max9820 ic. see table 1 for jumper ju1 configuration. gain setting the default gain-setting resistors (r1?4) configure the gain for both the left and right channels to -1v/v. the gain can be changed by replacing these resistors with other surface-mount 0603 resistors. resistors with a tol- erance of 1% or better are recommended for optimum performance. use table 2 and the following equations to select new gain-setting resistors for the correspond- ing channel. where rin is the respective input resistance, cin is the respective input capacitance, rfb is the respective feedback resistance, a is the desired gain, and -3db frequency is set at 20hz. the gain for either channel can be adjusted to a minimum of -1v/v. refer to the max9820 ic data sheet for more details. rin hz cin rfb k rin a > = ? 1 2 rfb 20 10 max9820 evaluation kit 2 _______________________________________________________________________________________ table 1. shutdown selection (ju1) shunt position shdn pin max9820 function installed connected to pgnd disabled not installed connected to vdd through resistor r5 enabled table 2. component function channel rin rfb cin right r2 r3 c2 left r1 r4 c1
evaluates: max9820 max9820 evaluation kit _______________________________________________________________________________________ 3 figure 1. max9820 ev kit schematic
evaluates: max9820 max9820 evaluation kit maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 4 ___________________ maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2009 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. figure 2. max9820 ev kit component placement guide component side figure 3. max9820 ev kit pcb layout?omponent side figure 4. max9820 ev kit pcb layout?older side
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