
1
VO_BT =
FB
R
V
1 +
V
÷
è
R +R
2
3
(1)
1
VO_BT =
FB
2
R
V
1 +
V
R
÷
è
(2)
LDO Voltage Regulators
Status Indicators
www.ti.com .......................................................................................................................................................................................... SLLS917 – SEPTEMBER 2008
PFM mode:
PWM mode:
Where:
VVO_BT: Voltage of VO_BT pin
VFB: Voltage of FB
pin defined by
reference voltage in
Electrical
Characteristics
The TPS65510 has four types of LDO voltage regulators; 1.2-V output (LDO1, shown in
Figure 3), 1.8-V output
(LDO2, shown in
Figure 3) and 3.3-V dual output (LDO3 and LDO4, shown in
Figure 3). These output voltage
are set by internal feedback loop only. The device has enable/disable control pin named V_CTRL for LDO1 and
LDO2. When the voltage of V_CTRL is low level, the device disables the output of LDO1 and LDO2. When the
voltage of V_CTRL is high level, the device enables the output of LDO1 and LDO2.
The power paths of LDO2, LDO3, and LDO4 are fixed; from output of LDO3 for LDO2 and from output of boost
converter for LDO3 and LDO4. The power path of LDO1 is selected by power path switch; when output voltage
of the boost converter is higher than the threshold specified by V(SW1) in Electrical Characteristics, the path
comes from output of LDO4. When output voltage of the boost converter is lower than the threshold specified by
V(SW1) in Electrical Characteristics, the path comes from backup battery connected to VBK pin.
The maximum outputs current are specified by I(VO1R2), I(VO1R8), I(VRO) and I(VOUT) in Electrical Characteristics.
The TPS65510 has two device status indicators; CS and XRESET. These signal pins consist of open drain of
N-ch MOSFET. Due to this, the pullup resistors should be needed. The recommended values of pullup resistors
are 100 k
.
CS function monitors the voltage level of VBAT pin and VO_BT pin for selecting power path of VOUT. When the
signal level of CS pin is high level, the power path of VOUT comes from the main battery via the boost converter.
When the signal level of CS pin is low level, it comes from backup battery except the starting operation of boost
converter. When the boost converter starts operation with the main battery, the P-ch MOSFET at LDO4 turns ON
to avoid supplying the power from backup battery even if the voltage of VOUT is lower than the threshold
specified by V(SW1) in Electrical Characteristics. The signal of the CS pin remains low level when the main battery
is removed (including the transition) or the voltage level of VOUT does not achieve the threshold specified by
V(SW2) in Electrical Characteristics.
XRESET function monitors the voltage level of VOUT pin for resetting the load like RTC. When the voltage of
VOUT is more than the threshold specified by V(XRESET_DET) and V(XRESET_HYS) in Electrical Characteristics, the
signal level of XRESET pin is high. When the voltage of VOUT is less than the threshold specified by
V(XRESET_DET) and V(XRESET_HYS) in Electrical Characteristics, the signal level of XRESET pin is low. This situation
requires resetting the load. The detailed waveform is shown in
Figure 5.Copyright 2008, Texas Instruments Incorporated
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