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19-2063; Rev 0; 6/01
MAX1778 Evaluation Kit
General Description
The MAX1778 evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board that contains a step-up switching regulator, two charge-pump voltageregulator circuits, a VCOM buffer, and a low-drop out linear regulator (LDO). The step-up switching circuit is configured for a +8V output that provides up to 250mA of current from a +3.0V supply. The EV kit can be powered from a +2.7V to +5.5V supply. The positive charge-pump circuit is configured for a +20V output that provides more than 10mA of current. The negative charge-pump circuit is configured for a -5V output and provides more than 20mA of current. Power for both charge-pump inputs is provided from the step-up switching regulator output. The EV kit also features an LDO linear regulator circuit, which is configured for a +2.5V output that provides more than 200mA of current. Power for the LDO regulator circuit is provided from the input supply. The VCOM buffer provides a +4V output and more than 150mA of peak current. The step-up switching regulator output provides power to the VCOM buffer. The MAX1778 EV kit demonstrates low quiescent current and high efficiency (over 91%). High-frequency operation (500kHz/1MHz) allows the use of tiny surfacemount components and fast transient response. The MAX1778 TSSOP package (1.1mm max) with low-profile external components allows this circuit to be less than 1.2mm in height. A built-in transient load tester facilitates transient load tests. The MAX1778 EV kit can also be used to evaluate the MAX1880, MAX1881, and MAX1882 ICs. o +2.7V to +5.5V Input Range o Output Voltages +8V, >200mA (Step-Up Switching Regulator) +20V, >10mA (Positive Charge-Pump Regulator) -5V, >20mA (Negative Charge-Pump Regulator) +2.5V, >200mA (LDO Linear Regulator) +4V, >150mA Peak (VCOM Buffer) o All Outputs Are Adjustable with Resistors o >91% Efficiency o Internal MOSFET Switches o <1A (typ) IC Shutdown Current o 1MHz Step-Up Switching Regulator Frequency o 500kHz Charge-Pump Regulator Switching Frequency o Adjustable Fault-Trip Level o Low-Profile External Components o Built-In Transient Load Tester o Surface-Mount Components o Fully Assembled and Tested
Features
Evaluates: MAX1778/MAX1880/MAX1881/MAX1882
Ordering Information
PART MAX1778EVKIT TEMP. RANGE 0C to +70C IC PACKAGE 24 TSSOP
Component List
DESIGNATION C1, C16, C17, C18, C21 QTY 5 DESCRIPTION 3.3F 10%, 10V X7R ceramic capacitors (1210) Taiyo Yuden LMK325BJ335KD 0.47F 10%, 10V X7R ceramic capacitor (0603) Taiyo Yuden LMK107BJ474KA 0.01F 10%, 50V X7R ceramic capacitors (0603) Murata GRM39X7R103K050AD 0.1F 20%, 16V X7R ceramic capacitors (0603) Taiyo Yuden EMK107BJ104MA DESIGNATION C5, C7, C11, C13, C25-C29 QTY 9 DESCRIPTION 1F 10%, 16V X7R ceramic capacitors (1206) Murata GRM42-6X7R105K016 1000pF 10%, 50V X7R ceramic capacitor (0603) Murata GRM39X7R102K050AD 0.22F 10%, 10V X7R ceramic capacitor (0603) Taiyo Yuden LMK107BJ224KA Not installed (0603)
C2
1
C8
1
C3, C14
2
C9
1
C12, C20, C24
0
C4, C6, C10, C22
4
________________________________________________________________ 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.
MAX1778 Evaluation Kit Evaluates: MAX1778/MAX1880/MAX1881/MAX1882
Component List (continued)
DESIGNATION C19 QTY 1 DESCRIPTION 470pF 5%, 50V COH ceramic capacitor (0603) Taiyo Yuden UMK107CH4715Z 3A, 30V Schottky diode (M-flat) Toshiba CMS02 200mA, 25V Schottky diodes (SOT23) Fairchild BAT54S 200mA, 75V ultra-fast diode (SOT23) Fairchild MMBD4148 6.8H inductor Coilcraft LPO25061B-682 30V, 11.5A, N-channel MOSFET (SOT223) Fairchild Semiconductor NDT455N 40V, 600mA, NPN transistor (SOT23) Central Semiconductor CMPT2222A 274k 1% resistor (0805) 49.9k 1% resistors (0805) 750k 1% resistor (0805) 200k 1% resistor (0805) 24k 5% resistor (0805) 100k 1% resistors (0805) 1M 5% resistor (0805) Not installed (0805) 10k 1% resistors (0805) 51 5% resistor (0805) 1.0 1%, 1W resistor (2010) IRC LRC-LR 2010-01-1R00-F 1.5k 5% resistor (0805) 10 5% resistor (0805) 10k 5% resistor (0805) MAX1778EUG (24-pin TSSOP) 2-pin header Shunt (JU1) MAX1778 PC board MAX1778 data sheet MAX1778 EV kit data sheet SUPPLIER Central Semiconductor Coilcraft Fairchild IRC Murata Taiyo Yuden Toshiba
Component Suppliers
PHONE 516-435-1110 847-639-6400 408-822-2000 512-992-7900 814-237-1431 408-573-4150 949-455-2000 FAX 516-435-1824 847-639-1469 408-822-2102 512-992-3377 814-238-0490 408-573-4159 949-859-3963
D1
1
D2, D3, D4
3
D5
1
Note: Please indicate that you are using the MAX1778, MAX1880, MAX1881, or MAX1882 when contacting these component suppliers.
L1
1
Quick Start
The MAX1778 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.
N1
1
Q1
1
Output Verification
1) Verify that jumper JU1 (SHDN) does not have a shunt across its pins. 2) Connect a voltmeter to the V1 pad. 3) Connect a +2.7V to +5.5V DC power supply to the PIN pad. Connect the supply ground to the GND pad. 4) Turn on the power supply, and verify that the main output (V1) is +8V. 5) Verify that the negative charge-pump regulator output (VN) is -5V. 6) Verify that the positive charge-pump regulator output (VP) is +20V. 7) Verify that the LDO output (LDOOUT) is +2.5V. 8) Verify that the V COM buffer output (BUFOUT) is +4V. For instructions on selecting the feedback resistors for other output voltages, see Evaluating Other Output Voltages. The input voltage range is +2.7V to +5.5V when selecting the output voltage.
R1 R2, R4, R6 R3 R5 R7 R8, R10, R12 R9 R11, R13, R16 R14, R15 R17 R18 R19 R20 R21 U1 JU1 None None None None
1 3 1 1 1 3 1 0 2 1 1 1 1 1 1 1 1 1 1 1
Detailed Description
The MAX1778 evaluation kit step-up switching regulator circuit can be configured for an output voltage up to +13V. A built-in transient load tester (TRANS_LOAD, CSEN) for the step-up switching regulator allows transient load tests up to 1A.
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MAX1778 Evaluation Kit
The positive charge-pump circuit can be reconfigured to provide up to +35V by changing feedback resistors, provided that the step-up switching regulator (V1) has been changed to a higher voltage. The negative charge-pump circuit can also be reconfigured to provide up to -11V by changing feedback resistors, provided that the step-up switching regulator (V1) has been adjusted to a higher voltage. The EV kit's LDO linear regulator circuit is configured for a +2.5V output (LDOOUT) at more than 200mA of current and can be reconfigured for other output voltages by replacing feedback resistors. When using an external transistor (Q1) for the LDO, regulator power for the LDO output is provided by PIN. When an external transistor (Q1) is not used, power is provided by the step-up switching regulator (V1). For even higher output current, the SOT23 NPN transistor (Q1) can be replaced with a larger D-PAK device. The VCOM buffer output (BUFOUT) is a scaled down voltage of the step-up switching regulator (V1) and can be reconfigured for other voltages by replacing the voltage-divider resistors (R10, R11). The step-up switching regulator provides power to the VCOM buffer. A separate analog ground pad (GND) for the VCOM buffer output is provided to reduce noise coupling to the output. The EV kit features an adjustable fault-trip level that can be reconfigured for different fault-trip levels. Unpopulated feedback-compensation PC board pads are provided for the step-up switching regulator. The linear regulator can be configured for different voltages and output currents. The MAX1778 EV kit can also evaluate the MAX1880, MAX1881, and MAX1882. Order the IC from the phone number listed on page 1, and replace the MAX1778 with the appropriate IC.
Evaluates: MAX1778/MAX1880/MAX1881/MAX1882
Table 1. Jumper JU1 Functions
SHUNT LOCATION None Installed SHDN PIN Connected to PIN through R8 Connected to GND MAX1778 OUTPUT Enabled Shutdown
to +10V, so replace them with higher voltage-rated capacitors for output voltages over 10V. Refer to the Output Voltage Selection section in the MAX1778 data sheet for instructions on selecting the resistors.
Positive Charge-Pump Output Voltages
The MAX1778 EV kit's positive charge-pump regulator output is set to +20V by feedback resistors (R3, R4). To generate output voltages other than +20V (up to +35V), select different external voltage-divider resistors (R3, R4). Refer to the Output Voltage Selection section in the MAX1778/MAX1880-MAX1885 data sheet for instructions on selecting the resistors. Check that the capacitor voltage rating is adequate for the configuration.
Negative Charge-Pump Output Voltages
The MAX1778 EV kit's negative charge-pump regulator output is set to -5V by feedback resistors (R5, R6). To generate output voltages other than -5V (down to -11V), select different external voltage-divider resistors (R5, R6). Refer to the Output Voltage Selection section in the MAX1778/MAX1880-MAX1885 data sheet for instructions on selecting the resistors.
LDO Regulator Output Voltages
The MAX1778 EV kit's LDO linear regulator output is set to +2.5V by feedback resistors (R14, R15). To generate output voltages other than +2.5V (+1.25V to V PIN -300mV), select different external voltage-divider resistors (R14, R15). Refer to the Output Voltage Selection section in the MAX1778 data sheet for instructions on selecting the resistors. The power dissipation of the NPN transistor (Q1, 350mW) must not be exceeded. If a larger transistor is required, a "DPAK" surface-mount case may be used to replace Q1 (MJD31, On Semiconductor, or similar recommended). Refer to the External Pass Transistor section in the MAX1778/ MAX1880-MAX1885 data sheet for instructions on selecting a transistor.
Jumper Selection Shutdown Mode
The MAX1778 EV kit features a shutdown mode that reduces the MAX1778 quiescent current. The 2-pin jumper (JU1) selects the MAX1778 shutdown mode. Table 1 lists the selectable jumper options.
Output Voltage Selection and Transient Load Test
Step-Up SwitchingRegulator Output Voltages
The MAX1778 EV kit's step-up switching-regulator output is set to +8V by feedback resistors (R1, R2). To generate output voltages other than +8V (up to +13V), select different external voltage-divider resistors (R1, R2). The ceramic capacitors (C17, C18, C21) are rated
VCOM Buffer Output Voltages
The MAX1778 EV kit's VCOM buffer output (BUFOUT) is configured to one half of V1's output voltage (i.e., 0.5 8V = +4V) by using the MAX1778 IC's internal 0.5 volt3
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MAX1778 Evaluation Kit Evaluates: MAX1778/MAX1880/MAX1881/MAX1882
age divider. Select different external voltage-divider resistors (R10, R11) to generate output voltages other than +4V (+1.2V to +(VSUPB - 1.2V)). Refer to the Output Voltage Selection section in the MAX1778/MAX1880-MAX1885 data sheet for instructions on selecting the resistors. The VCOM buffer has a separate analog ground pad (GND) next to the VCOM buffer output (BUFOUT) to reduce any noise coupling.
Maximizing Transient Performance
The MAX1778 EV kit features several surface-mount, unpopulated PC board pads for installing feedback compensation components (R7, C19, C20). To maximize the transient load performance, remove capacitor C8, connect the INTG pin (pin 2) to the REF pin (pin 9) of IC U1, and remove resistor R7 and capacitor C19. Refer to the Feedback Compensation section in the MAX1778/MAX1880-MAX1885 data sheet for instructions on selecting other resistors and capacitors.
Transient Load Tester
The MAX1778 EV kit features a built-in transient load tester for the step-up switching regulator. Connect a square-wave function generator (50 output) to the TRANS_LOAD and GND pads. Set the frequency and duty cycle as required. Note that varying the function generator output voltage (2.0V typ to 10V max) will vary the gate drive and thus will vary the amount of load connected to V1. Set the low and high voltage of the square-wave output according to the desired low- and high-load currents. Load currents can be calculated by measuring the voltage at the CSEN pad (across R18, 1) and GND. Divide the measured voltage by 1 to obtain the actual load current.
Evaluating Other ICs and Different Linear Regulator Configurations
Evaluating a MAX1880, MAX1881, or MAX1882
The MAX1778 EV kit can be reconfigured for evaluating the MAX1880, MAX1881, and MAX1882 ICs. U1 (MAX1778) must be removed and replaced with the new IC (24-pin TSSOP package). The linear regulator will not function when evaluating a MAX1880 or MAX1882. Refer to the MAX1778/MAX1880-MAX1885 IC data sheet for information on the various step-up switching frequency and LDO features.
Faults and Maximizing Transient Performance
Fault-Trip Level
The MAX1778 EV kit's fault-trip level for the step-up switching regulator and the positive charge pump is configured for a +1.1V (0.67 VREF to 0.87 VREF) fault-trip level. To reconfigure the EV kit for other fault-trip levels (+0.84V to +1.09V), select different external voltagedivider resistors (R12, R13). Refer to the Fault-Trip Level (FLTSET) section in the MAX1778/MAX1880-MAX1885 data sheet for instructions on selecting the resistors.
Linear Regulator Voltages
The MAX1778 EV kit can be reconfigured for evaluating other linear regulator voltages and currents. Several components must be replaced to obtain higher voltages or currents. Table 2 lists the components to replace.
Table 2. Component List for Evaluating Other Linear Regulators
DESIGNATOR LDO Output Voltage (LDOOUT) LDO Output Current (LDOOUT) Q1 (external NPN) C3 C14 C27 C29 R14 R15 R16 R19 CASE 1 +7.6V (V1 set to 8V) 40mA Not installed Not installed Not installed 3.3F Not installed 10k 51.1k 0 13k CASE 2 +9V to +12.4V (V1 set to 13V) 40mA Not installed Not installed Not installed 2.2F Not installed 10k 60k to 89k 0 13k CASE 3 +3.3V 300mA to 500mA D-PAK (MJD31) 0.01F 0.01F 1.0F 1.0F 10k 16.5k Not installed 4.02k CASE 4 +2.5V 200mA SOT23 (2N2222A) 0.01F 0.01F 1.0F 1.0F 10k 10k Not installed 3.01k
4
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PIN
L1 6.8H D1
V1 +8V
GND D5 4 N1 23 TGND 3 R2 R7 24k C19 470pF D4 2 R C5 1.0F L1 V1 C11 1.0F VP +20V V1 17 SUPN BUF+ C10 0.1F D2 2 R L1 5 BUFOUT 7 BUFOUT FLTSET 18 DRVN FBP FBN GND 8 R3 750k 1% C14 0.01F 10 R13 OPEN REF R12 100k 1% 16 FBLDO FBL 15 BUFPIN C12 OPEN V1 Q1 C22 0.1F R16 OPEN 1 3 L C13 1.0F 16V 2R LDOOUT +2.5V R15 10k 1% C3 0.01F C29 1.0F 16V GND PIN 24 3 RDY C4 0.1F SUPP V1 4 R11 OPEN 6 SUPB RDY C25 1.0F R9 1M 19 3 C20 OPEN R18 1.0 1% R21 10k GND FB CSEN R17 51 1 1 3 L TRANS_LOAD 2 1 3 IN LX C2 0.47F 22 R1 274k 1% C17 3.3F 10V C18 3.3F 10V C21 3.3F 10V
Figure 1. MAX1778 EV Kit Schematic
C16 3.3F 10V R20 10 2 C8 1000pF INTG PGND 21 R2 49.9k 1%
C1 3.3F 10V
C24 OPEN R10 100k 1% V1
U1 MAX1778
DRVP
20
GND
GND C6 0.1F 3
2
D3
R
C26 1.0F 16V
VN -5V 11 R6 49.9k 1% 9 REF LDOOUT C27 1.0F 16V SHDN SUPL 13 C28 1.0F 16V V1 14 C9 0.22F 12 JU1 R4 49.9k 1% REF
1L
C7 1.0F
R5 200k 1%
R14 10k 1%
PIN
R8 100k 1%
R19 1.5k
FBLDO
Evaluates: MAX1778/MAX1880/MAX1881/MAX1882
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NOTE: REMOVE C8, R7, AND C19, AND SHORT U1-2 (INTG) TO U1-9 (REF) FOR IMPROVED TRANSIENT RESPONSE.
MAX1778 Evaluation Kit
5
MAX1778 Evaluation Kit Evaluates: MAX1778/MAX1880/MAX1881/MAX1882
1.0"
1.0"
Figure 2. MAX1778 EV Kit Component Placement Guide-- Component Side
Figure 3. MAX1778 EV Kit PC Board Layout--Component Side
1.0"
Figure 4. MAX1778 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) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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