
TCA5600 TCF5600
10
MOTOROLA ANALOG IC DEVICE DATA
Programmable Voltage Regulator
This series voltage regulator is programmable by the
voltage divider R4, R5 for a nominal output voltage of 6.0 V
≤
Vout2
≤
30 V.
(Vout2 – Vref nom)
R5
Vref nom
(7)
R4 =
[R5 = 10 k, Vref nom = 2.5 V]
Current limitation and thermal shutdown capability are
standard features of this regulator. The voltage drop
V(Pin 9 – Pin 8) across the series pass transistor generates
the feedback signal to control the dc/dc converter
(see Figure 13).
Control Inputs INH1, INH2
The dc/dc converter and/or the regulator Vout2 are remote
controllable through the TTL, MOS compatible inhibit inputs
INH1 and INH2 where the latter is a three–level detector
(Logic “0”, High Impedance “Z”, Logic “1”). Both inputs are
set–up to provide the following truth table:
Figure 15. INH1, INH2 TruthTable
Mode
INH1
INH2
Vout2
OFF
Vout2
Vout2
OFF
5.0 V
5.0 V
DC/DC
1
2
3
4
5
6
0
0
0
1
1
1
0
INT
ON
INT
INT
ON
INT
High “Z”
1
0
High “Z”
1
INT:
Intermittent operation of the converter means that the
converter operates only if VCC2<Vout2.
The converter loads the storage capacitor C2 to its full
charge (V9 = 33 V), allowing fast response time of the
regulator Vout2 when addressed by the control software.
High impedance (internal resistor 10 k to ground)
ON:
OFF:
Figure 16 represents a typical timing diagram for an E2PROM
programming sequence in a microprocessor based system.
The High “Z” state enables the dc/dc converter to ramp during
t3 to the voltage V9 at Pin 9 to a high level before the write
cycle takes place in the memory.
V9
VCC2
V9 max
– VF
Vout2
5.0V
INH1
“1”
”0”
INH2
“1”
“0”
High “Z”
t3
t4
V9 int
t
Programming
Voltage VPP
Figure 16. Typical E2PROM Programming Sequence
(not to scale)
Microprocessor Supply Regulator
Together with an external PNP power transistor (Q1), a
5.0 V supply exhibiting low voltage drop is obtained to power
microprocessor systems and auxiliary circuits. Using a power
Darlington with adequate heat sink in the output stage boosts
the output current Iout1 above 1.0 A.
The current limitation circuit measures the emitter current
of Q1 by means of the sensing resistor, RSC:
VRSC
(8)
RSC =
IE
[IE: emitter current of Q1]
[VRSC: threshold voltage
[VRSC:
(see Electrical Characteristics Table)]
The voltage protection circuit performs a foldback
characteristic above a nominal operating voltage, VCC2
≥
18 V.
Delay and Watchdog Circuit
The undervoltage monitor supervises the power supply
Vout1 and releases the delay circuit RESET as soon as the
regulator output reaches the microprocessor operating a
range [e.g., Vlow 0.93
Vout1(nom)]. The RESET output has
an open–collector and may be connected in a “wired–OR”
configuration.
The watchdog circuit consists of a retriggerable
monostable with a negative edge sensitive control input WDI.
The watchdog feature may be disabled by means of the
watchdog select input WDS driven to a “1”. Figure 17 displays
the Typical RESET Timing Diagram.
The commuted current source IC5 on Pin 17, threshold
voltage VC5(L), VC5(H) and an external capacitor C5 define
the RESET delay and the watchdog timing. The relationship
of the timing signals are indicated by the Equations (9) to (11).
(9)
RESET delay:
td =
C5
VC5(H)
|IC5|
Watchdog timeout:
Watchdog RESET:
twd =
tr =
C5
(VC5(H) – VC5(L))
5
IC5
C5
(VC5(H) – VC5(L))
50
|IC5|
(10)
(11)
[IC5, VC5(H), VC5(L): see Electrical Characteristics Table]