HMC10XX FAMILY
9
Single Clock Circuitry—Some form of clock is needed to
trigger the set and reset pulses (Figure 5) to create the
switching signal. The circuit shown in Figure 7 can be used
to create a strong (>4Amp) pulse. The diodes, resistors,
capacitors and inverters basically create the TRS and the
TSR delays. Now a single signal (Clock) can trigger a set or
reset pulse. The minimum timing between the rising and
falling edges of Clock are determined by the 25K
and 1nF
time constant. That is, the minimum high and low time for
Clock is
≈
25
μ
s.
Micro Processor—The circuit in Figure 8 generates a strong
set/reset pulse (>4 Amp) under microprocessor control. The
T
SR
T
RS
SET
RESET
S/R
16V
-16V
T
RS
≥
5 μsec
T
SR
≥
5 μsec
T
PW
≈
2 μsec
5V
T
PW
set
reset
S/R strap @ 4.5
typ.
3A peak (min.)
SET
10K
1
0.22μF
4.7μF (1)
25K
+16 to 20V
17
HMC2003
2N3904
RESET
S/R
I
1
2
4
3
5,6
7,8
(1) Tantalum, low R
(2) HEXFETs with
≈
0.2
Ron
25K
0.1μF
Figure 8—Set/Reset Circuit With Microprocessor Control(1001/1002)
SET and RESET signals are generated from a
microprocessor and control the P and N channel HEXFET
drivers (IRF7106). The purpose of creating the TRS and the
TSR delays are to make sure that one HEXFET is off before
the other one turns on. Basically, a break-before-make
switching pattern. The current pulse is drawn from the 4.7
μ
F
capacitor. If the 5V to 20V converter is used as shown in
Figure 6, then the resultant noise and droop on the 16-20V
supply is not an issue. But if the 16-20V supply is used
elsewhere in the system, then a series dropping resistor
(
≈
500
) should be placed between the 4.7
μ
F capacitor and
the supply.time constant. That is, the minimum high and low
time for Clock is
≈
25
μ
s.
MAX662A
Clock
S/R
16V
-16V
T
PW
≈
2 μsec
5V
set
reset
Figure 5—Single Clock Set/Reset Timing
Figure 6—5V to 20V Converter
0.22μF*
1
2
8
7
5
SHDN
GND
Vcc
C1-
C1+
1μF
Vout
4
3
C2+
C2-
0.22μF*
1μF
1N5818
20V
6
5V
* Use tantalum capacitors
12V
2μF
1μF
10K
25K
+16 to 20V
2N3904
25K
0.1μF
S/R strap @ 4.5
typ.
3A peak (min.)
Clock
1
0.22μF (2)
4.7μF (3)
17
HMC2003
S/R
(1) HEXFETs with
≈
0.2
Ron
(2) 0.22μF Tantalum or a
0.68 μF Ceramic CK06
(3) Tantalum, low R
25K
25K
1nF
1nF
8
9
4
3
2
1
6
5
7
14
5V
74HC04
1N4001
I
1
2
4
3
5,6
7,8
Figure 7—Single Clock Set/Reset Pulse Circuit (1001/1002)