Time Base - LeCroy WaveSurfer 400 Series Service Manual

4.2.4 Time Base

The time base includes four circuits:
• MCG426:
• MTB411A: Time Base System
• TDC:
• MST429A: generates main trigger signal for Time Base system.
Analog Control
Circuit name signal level
MST REF1 +/-4V
MST REF2 +/-4V
MST REF3 +/-4V
MST REF4 +/-4V
TDC ADJ 0 to +4V
Vcc
enable
clock 10MHz
clock 10MHz
clock 500MHz
DIO(7:0) +
CONTROL
A(1:0) +
from uP
control
TRT
to trigger selection
EXTCK
EXTREF
10 MHz
Reference
generates sampling clocks: 12.5 MHz up to 2GHz
generates clocks for the MTB411
interleaves sampling clocks to increase sampling rate and memory
depth.
Trigger circuitry
Main oscillator circuitry
Frequency divider for a Probe Calibrator
Time to Digital Converter interpolator and Real Time computation
voltage
Reference signal for analog time of Smart trigger
Reference signal for analog time of Smart trigger
Reference signal for analog time of Smart trigger
Reference signal for analog time of Smart trigger
TDC gain control signal
ENABLE
Q D
BCK
Q
MST 429
TRIG
2
2
R
IT
RT
TR
TRIG RAMPST A C
C
IG
M
K
K
S2EDGE D
PS
FDCK
EN10MHZ
FDEND
10MHZ
500MHZ
MACQ
MCG 426
TSCK
TBCK
SHCK_A
TRT
SHCK_B
2
EXTCK SHCK_C
SHCK_D
EXTREF
INTREF MCLR
PHDET VCO2G PDCK
2
2
2
VCO
Figure 4-8 Time Base Block Diagram
Signal name
TRIGEN
ITBUSY
TRIGD
ITCK
MTB 411
RTCK
MACQ
INT
FDCK FDEND
TSCK TBCK
2
SHCK_A
SHCK_B 2
2
SHCK_C
HSH & ADC
SHCK_D 2
CLR
MCK
Peak
Detect
MPD
_ITMB
to uP
MEMORY
MCK
DIN[7..0]
Theory of Operation 4-9