Datasheet

INH/UVLO
VIN
PVIN
R
UVLO1
R
UVLO2
> 4.5 V
INH/UVLO
PVIN
VIN
R
UVLO1
R
UVLO2
INH/UVLO
PVIN
VIN
R
UVLO1
R
UVLO2
LMZ31710
www.ti.com SNVS987A –JULY 2013–REVISED JULY 2013
Programmable Undervoltage Lockout (UVLO)
The LMZ31710 implements internal UVLO circuitry on the VIN pin. The device is disabled when the VIN pin
voltage falls below the internal VIN UVLO threshold. The internal VIN UVLO rising threshold is 4.5 V(max) with a
typical hysteresis of 150 mV.
If an application requires either a higher UVLO threshold on the VIN pin or a higher UVLO threshold for a
combined VIN and PVIN, then the UVLO pin can be configured as shown in Figure 43 or Figure 44. Table 10
lists standard values for R
UVLO1
and R
UVLO2
to adjust the VIN UVLO voltage up.
Figure 43. Adjustable VIN UVLO Figure 44. Adjustable VIN and PVIN Undervoltage
Lockout
Table 10. Standard Resistor values for Adjusting VIN UVLO
VIN UVLO (V) 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0
R
UVLO1
(kΩ) 68.1 68.1 68.1 68.1 68.1 68.1 68.1 68.1 68.1 68.1 68.1
R
UVLO2
(kΩ) 21.5 18.7 16.9 15.4 14.0 13.0 12.1 11.3 10.5 9.76 9.31
Hysteresis (mV) 400 415 430 450 465 480 500 515 530 550 565
For a split rail application, if a secondary UVLO on PVIN is required, VIN must be ≥ 4.5V. Figure 45 shows the
PVIN UVLO configuration. Use Table 11 to select R
UVLO1
and R
UVLO2
for PVIN. If PVIN UVLO is set for less than
3.0 V, a 5.1-V zener diode should be added to clamp the voltage on the UVLO pin below 6 V.
Figure 45. Adjustable PVIN Undervoltage Lockout, (VIN ≥4.5 V)
Table 11. Standard Resistor Values for Adjusting PVIN UVLO, (VIN ≥4.5 V)
PVIN UVLO (V) 2.9 3.0 3.5 4.0 4.5
R
UVLO1
(kΩ) 68.1 68.1 68.1 68.1 68.1
For higher PVIN UVLO voltages see
R
UVLO2
(kΩ) 47.5 44.2 34.8 28.7 24.3
Table 10 for resistor values
Hysteresis (mV) 330 335 350 365 385
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