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
LMZ31707
SLVSBV7A –JUNE 2013–REVISED AUGUST 2013 www.ti.com
Programmable Undervoltage Lockout (UVLO)
The LMZ31707 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 40 or Figure 41. Table 10
lists standard values for R
UVLO1
and R
UVLO2
to adjust the VIN UVLO voltage up.
Figure 40. Adjustable VIN UVLO Figure 41. 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 42 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 42. 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
24 Submit Documentation Feedback Copyright © 2013, Texas Instruments Incorporated
Product Folder Links: LMZ31707