DEMO MANUAL DC052A LTC1410 12-Bit, High Speed, 1.25Msps A/D Converter Demo Board Description The LTC 1410 is a 650ns, 1.25Msps, sampling 12-bit analog input range information. Additionally, a schematic, A/D converter which draws only 160mW from 5V parts list, drawings and dimensions of all the PC board supplies. The LTC1410 demo board provides the user with layers are included. An explanation of the layout and by- a way to evaluate the LTC1410 high speed A/D converter. pass strategies used in this board is also included so that In addition, the LTC1410 demo board is intended to anyone designing a PC board using the LTC1410 will be illustrate the layout and bypassing techniques required to able to get the maximum performance from the device. obtain optimum performance from this part. The LTC1410 Some key features of this demo board include: demo board is designed to be easy to use and requires Proven 1.25Msps 12-bit ADC surface mount layout only 7V to 15V supplies, a conversion start signal and 2 an analog input signal (single-ended or differential). As Actual ADC footprint only 0.5 inch including bypass shown in the board photo, the LTC1410 is a very space capacitors efficient solution for A/D users. By combining a 12-bit 72dB SINAD and 82dB THD at 600kHz inputs A/D, sample-and-hold, reference and clock circuitry into a single SOIC package, all the data acquisition circuitry Design files for this circuit board are available at including the bypass capacitors can be placed into an area DEMO MANUAL DC052A o OPera Ting TH e BOar D These values can be altered to meet other circuit and input signal requirements. For lower bandwidth input signals, Powering the Board increase C8s value. For undersampling applications that take advantage of the input circuitrys wide bandwidth, To use the demo board, apply 7V to 15V at 200mA to decrease the capacitance of C8. the banana jacks J1 and J2 and 0V (GND) to J3. Be careful to observe the correct polarity. Internal regulators provide The best way to observe the performance of the LTC1410 5V to the LTC1410. An LT1121-5 regulator (U7) provides is by directly driving it from a low impedance signal source. 5V for analog and digital circuitry while 5V is provided However, since some applications involve high output for the A/D and buffer by the MC79L05 regulator (U6). impedance sources, the board also has provisions for an onboard LT1360 high speed operational amplifier. The The analog input buffer is recommended if the source impedance of the input signal is greater than 930. The LT1360, operat - The LTC1410 has a unique feature not found on previ- ing as a noninverting buffer, provides the LTC1410 with ous ADCs: differential inputs with good common mode a fast settling, low impedance signal that allows the input rejection from DC to over 10MHz. While this feature is voltage to fully settle before starting a conversion. The extremely valuable for rejecting noise and measuring dif- LT1360 demonstrates an example of properly driving the ferential signals, the board can also be used to evaluate LTC1410. When using the LT1360, open JP1 and close the LTC1410 in single-ended mode (with the input JP2 and JP6. grounded). This board allows evaluation in either mode. Optimum performance is achieved using a signal source Differential (bipolar) analog signals are applied to the that has low output impedance, is low noise and has LTC1410 demo board using BNC connectors J4 (non- low distortion. Signal generators, such as the B&K Type inverting + input) and J5 (inverting input). The analog 1051 Sine Generator, give excellent results. Further, this signal input range is 2.5V. generator can be configured to operate referenced to a The LTC1410 +A (noninverting) and A (inverting) IN IN master clock signal, as shown in Figure 1. inputs have a common-mode range of V to V . The SS DD full-scale differential between the signals applied to +A IN REFERENCE and A is 2.5V. For example, when a 1.5V signal is IN FREQUENCY BRUEL & KJAER V IN IN applied to the A input, the negative-to-positive full- IN TYPE 1051 SINE GENERATOR scale input range of +A is 1V to 4V, corresponding to J2 IN E5 1-12 HEWLETT PACKARD an output code of 1000 0000 0000 to 0111 1111 1111. LTC1410 HP1663A D 12-BIT A/D OUT LOGIC DEMO BOARD The demo board is delivered with jumpers JP1 and JP2 ANALYZER closed. This configures the board for a 2.5V input signal HEWLETT PACKARD CLOCK J1 CONVST CLK centered around ground and applied to J4 (+A ). IN HP3326A REFERENCE GENERATOR FREQUENCY The board includes a recommended lowpass filter (R1, R4, OUT dc052a F01 and C8) across the differential inputs. With the component values shown, the cutoff frequency (f ) is: s Figure 1. Typical Setup for LTC1410 Demo Board 1 = 1.56MHz 2(102) (0.001F) dc052af 2 peration