X80000 Datasheet, PDF (17/37 Pages) Intersil Corporation – Smart Power Plug Penta-Power Sequence Controller with Hot Swap

X80000, X80001
Overvoltage and Undervoltage Shutdown
The X80000 provides overvoltage and undervoltage
protection circuits.
When an overvoltage (V_OV) or undervoltage (V_UV1 and
V_UV2) condition is detected, the GATE pin will be
immediately pulled low. The undervoltage threshold V_UV1
applies to the normal operation with a main supply. The
undervoltage threshold V_UV2 assumes the system is
powered by a battery. When using a battery backup, the
BATT-ON pin is pulled to V_RGO. The default thresholds have
been set so the external resistance values determine the
overvoltage threshold, a main undervoltage threshold and a
battery undervoltage threshold.
As shown in Figure 26, this circuit block contains
comparators and programmable voltage references to
monitor the single overvoltage and dual undervoltage trip
points. During manufacturing, Intersil programmed the
overvoltage and undervoltage trip points as shown in Table 1
below. Custom values are possible.
A resistor divider connected between the plus and minus
input voltages and the V_UV/OV pin (see Figure 24)
determines the overvoltage and undervoltage shutdown
voltages and the operating voltage range. Using the
thresholds in Table 1 and the equations of Figure 24 the
desired operating voltage can be determined. Figure 25
shows the resistance values for various operating voltages.
TABLE 1. OVERVOLTAGE/UNDERVOLTAGE DEFAULT
THRESHOLDS
THRESHOLD
SYMBOL
DESCRIPTION
FALLING RISING
MAX/MIN
VOLTAGE
(Note 1)
LOCKOUT
VOLTAGE
(Note 2)
V_OV Overvoltage 3.87V 3.9V 74.3
74.9
(X80000)
V_OV Overvoltage 3.51V 3.54V 67.4
68
(X80001)
V_UV1 Undervoltage 2.21V 2.24V 43.0
42.4
1
V_UV2 Undervoltage 1.73V 1.76V 33.8
33.2
2
NOTES:
1. Max/Min Voltage is the maximum and minimum operating voltage
assuming the recommended V_UV/OV resistor divider.
2. Lockout voltage is the voltage where the X80000/1 turns off the
FET.
V_P
V_S
R1
V_UV/OV
Voltage divider:
V_{UV ⁄ OV} = V_{SR}-----₁---^R--₊---²--_R-----₂--_
or:
R2
V_N
V_S
=
V_UV
⁄

OV
R_-----1_---R--+_---2--R_-----2_{--}
FIGURE 24. OVERVOLTAGE UNDERVOLTAGE DIVIDER
100
90
80
70 ^VOV
60
50 _VUV1
40
30
20 ^VUV2
10
0
BATT-ON = V_EE
Operating
Voltage
BATT-ON = V_RGO
R1 in kΩ (for R2=10K)
FIGURE 25. OPERATING VOLTAGE vs RESISTOR RATIO
Battery Back Up Operations
An external signal, BATT-ON, is provided to switch the
undervoltage trip point. The BATT-ON signal is a LOGIC
HIGH if V_IHB > V_EE + 4V and is a LOGIC LOW if V_ILB < V_EE
+ 2V. The time from a BATT-ON input change to a valid new
undervoltage threshold is 100ns. See Electrical
Specifications for more details.
Note: The V_UV/OV pin must be limited to less than V_EE +
5.5V in worst case conditions. Values for R1 and R2 must be
chosen such that this condition is met. Intersil recommends
R1 = 182kΩ and R2 = 10kΩ to conform to factory settings.
TABLE 2. SELECTING BETWEEN UNDERVOLTAGE TRIP
POINTS
PIN
DESCRIPTION
TRIP POINT SELECTION
BATT-ON
Undervoltage Trip If BATT-ON = 0,
Point Selection Pin V_UV1 trip point is selected;
If BATT-ON = 1,
V_UV2 trip point is selected.
V_UV1 and V_UV2 are undervoltage thresholds.
Overvoltage/Undervoltage Fault Condition Flags
On any overvoltage or undervoltage violation, the X80000
cuts-off the GATE. This condition also sets the fault-
overvoltage (FOV) or fault-undervoltage1/2 (FUV1/2) bits
low. These bits are readable through the SMBus. To clear
the fault bits, the fault condition must first be rectified (by the
17
FN8148.0
March 18, 2005