MAX6852 MAXIM [Maxim Integrated Products], MAX6852 Datasheet - Page 19

• Manufacturer Part Number: MAX6852
• Description: 4-Wire Interfaced, 5 x 7 Matrix Vacuum- Fluorescent Display Controller
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 14 shows the external components required for
the filament driver using a FET bridge.
PHASE1 and PHASE2 can be individually programmed
as one of four output types (Tables 36, 37).
When using the filament drive, first ensure that the fila-
ment duty-cycle register 0x09 is set to the correct value
before configuring the PHASE1 and PHASE2 outputs to
be filament drives. To stop the filament drive, program
either PHASE1 or PHASE2 (or both) to be logic-low gen-
eral-purpose outputs. Both PHASE1 and PHASE2 out-
puts come out of power-on-reset in logic-low condition.
The PUMP output can be programmed as one of four
output types (Table 38).
PORT0 and PORT1 can be individually programmed as
one of eight output types (Tables 39, 40). The PORT1
choices are similar to the PORT0 choices, except that
the last four items are invert logic. PORT0 output comes
out of power-on-reset in logic-low condition, whereas
PORT1 output initializes high.
Figure 12. Relationship Between Segment Output and VFD
Tube 5
✕
7 Matrix Dots
SEG 26
SEG 21
SEG 31
SEG 11
SEG 16
SEG 1
SEG 6
1-1
1-6
1-2
1-5
1-7
1-3
1-4
SEG 27
SEG 32
SEG 12
SEG 17
SEG 22
PHASE1 and PHASE2 Outputs
SEG 2
SEG 7
2-1
2-6
2-7
2-2
2-3
2-4
2-5
______________________________________________________________________________________
4-Wire Interfaced, 5
PORT0 and PORT1 Outputs
CURSOR
SEG 18
SEG 23
SEG 28
SEG 33
SEG 13
SEG 3
SEG 8
3-1
3-4
3-5
3-6
3-7
3-2
3-3
SEG 29
SEG 34
SEG 24
SEG 14
SEG 19
SEG 4
SEG 9
4-6
4-7
4-1
4-2
4-5
4-3
4-4
PUMP Output
SEG 30
SEG 15
SEG 20
SEG 25
SEG 35
SEG 10
SEG 5
5-6
5-4
5-1
5-2
5-3
5-5
5-7
Fluorescent Display Controller
The PORT0 and PORT1 shutdown outputs allow exter-
nal hardware (for example, a DC-DC converter power
supply for VFD) to be disabled by the MAX6852 when
the MAX6852 is shut down.
The 625Hz, 1250Hz, and 2500Hz outputs can drive a
piezo sounder either from PORT0 or PORT1 alone, or
by both ports together as bridge drive. For bridge
drive, the sounder is connected between PORT0 and
PORT1, taking advantage of the PORT1 output being
inverted with respect to PORT0. Select different fre-
quencies for PORT0 and PORT1 to obtain a wider
range of sounds when bridge drive is used.
The OSC1 and OSC2 inputs set the multiplex and blink
timing for the display driver. Connect an external resis-
tor from OSC2 to GND and an external capacitor C
from OSC1 to GND to set the frequency of the internal
RC oscillator. Alternatively, overdrive OSC1 with an
external TTL or CMOS clock. If an exact blink rate or
multiplex period is required, use an external clock
ranging between 2MHz and 8MHz to drive OSC1.
Figure 13. Filament Bridge Driver Timing Waveforms
Figure 14. Filament Bridge Driver (MOSFET)
PHASE 1
PHASE 2
PHASE 1
PHASE 2
✕
(A)
Multiplex Clock and Blink Timing
Q1
7 Matrix Vacuum-
R2
100µs MULTIPLEX TIME PERIOD (OSC = 4MHz)
GND
Q2
(B)
VFIL
(C)
Q3
Q4
GND
(D)
R4
VFD TUBE
(E)
OSC
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