PT6703 Datasheet, PDF (4/7 Pages) Texas Instruments – 13-A Low-Voltage Programmable Integrated Switching Regulator

Application Notes
PT6701/6702/6703, & PT6721/6722
Operating Features of the Programmable
PT6700 “Excalibur™” Series ISRs
Power Good
Programmable versions of the PT6700 Series regulators
incorporate a PWR Good output (pin 2). This output is
open-drain and generates an acitve-high signal when the
sensed output from the ISR is within a nominal ±10% of
the programmed set point. When the regulated output is
outside this range, pin 2 asserts a logic low (typically <0.1V). A
10-kΩ pull-up resistor to a valid bus voltage is required.
If the power good feature is not used, the pull-up resistor
can be omitted. The maximum voltage that may be ap-
plied to the pull-up resistor is 15V.
Over-Voltage Protection (OVP)
The PT6700 programmable regulators also incorporate
an OVP function. The OVP DRV (pin 1) normally has a
logic low output (typically <0.1V). When the ISR’s sensed
output exceeds the programmed output setting by 15%,
pin 1 produces a 60mA, +12V drive signal. This drive
signal can trigger an SCR, which can be used to disable
the input voltage (via a fuse), or alternatively interface to
another external monitoring device. When the ISR output
voltage returns to within 15% of its programmed setting,
pin 1 reverts back to its low state. If the OVP function is
not used, pin 1 may be left open circuit.
Stand-By Function
The PT6700 series ISRs incorporate a standby function.
This feature may be used for power-up sequencing, or
wherever there is a requirement for the output voltage
to be controlled by external circuitry.
If the STBY* input (pin 8) is left open-circuit the regulator
operates normally, providing a regulated output when a
valid supply voltage is applied to V_in (pins 10-12) with
respect to GND (pins 14-18). Connecting pin 8 to ground¹
places the regulator in standby mode ², and reduces the input
current to typically 20mA (30mA max). Applying a ground
signal to pin 8 prior to power-up, will disable the output
during the period that input power is applied. To ensure
that the regulator output is properly enabled, pin 8 must
be open circuit.
Table 1 Standby Control Requirements ²
Parameter
Min
Typ
Max
Enable
Open Cct. ¹
Disable
-0.1V
0.4V
1.0V
I_stby
10µA
Figure 1
5V
R1
10k
Pwr
Good
Inhibit
COM
76543
VID4 - VID0
1
OVP
23
SNS(+)
10-12
Vin
+
C _in
Pwr
Good
2
PT6700
19-22
Vo
STBY
8
GND
SNS(-)
14-18
13
+
C _out
Q1
BSS138
OVP DRV
V =2.5V
o
L
O
A
D
COM
Notes:
1. The standby on a PT6700 series regulator must be controlled
with an open-drain low-leakage (<100nA) MOSFET (See
fig. 1). Table 1 gives the threshold requirements. Do Not use a
pull-up resistor. The control input has an open-circuit voltage of
between 4Vdc and 5Vdc. To set the regulator output to zero,
the control pin must be “pulled” to less than 1.0Vdc by sinking
current to ground.
2. When placed in the standby mode, the regulator output may
assert a low impedance to ground. If an external voltage is
applied to the output, it will sink current and possibly over-
stress the part.
Turn-On Time
Turning Q₁ in Figure 1 off, removes the low-voltage signal
at pin 8. After a 10-15ms delay the regulator output
rises and reaches full output voltage within 30ms. Fig. 2
shows the typical waveforms of a PT6701 following the
prompt turn-off of Q₁ at time t =0 secs. The output volt-
age was set to 2.5V, and the waveforms were measured
with a 5V input source, and 10A resistive load.
Figure 2
Vout (2V/Div)
Iin (5A/Div)
VPWGD (10V/Div)
0
5
10
15
20
25
30
35
40
t (milli - secs)
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