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Positive Charge Pump

Negative Charge Pump

Linear Regulator Controller

Soft Start

Fault Protection

TPS65100, TPS65101

TPS65105

SLVS496C – SEPTEMBER 2003 – REVISED APRIL 2006

DETAILED DESCRIPTION (continued)

pump comes up next. The negative charge pump starts with a soft start and when the output voltage has

reached 91% of the nominal value, the positive charge pump comes up with a soft start. The VCOM buffer is

enabled as soon as the positive charge pump has reached its nominal value and VCOMIN is greater than

typically 1.0 V. Pulling the enable pin low shuts down the device. Depended on load current and output

capacitance, each of the outputs goes down.

charge pump is capable of supplying a minimum load current of 20 mA. Depending on the voltage difference

The TPS6510x series has a regulated negative charge pump using two external Schottky diodes. The input

voltage for the charge pump is applied to the SUP pin that is connected to the output of the main boost

currents are possible. See Figure 12.

The TPS6510x series includes a linear regulator controller to generate a 3.3-V rail which is useful when the

system is powered from a 5-V supply. The regulator is independent from the other voltage rails of the device and

has its own enable (ENR). Since most of the systems require this voltage rail to come up first it is recommended

to use a R-C delay on EN. This delays the start-up of the main boost converter which will reduce the inrush

current as well.

The main boost converter as well as the charge pumps, linear regulator, and VCOM buffer have an internal soft

during start-up caused by high inrush currents. See Figure 10 and Figure 11. During softstart of the main boost

where the current limit is set to 2/5 of the typical current limit (2/5 of 2.3A) for 1024 clock cycles then increased

to 3/5 of the current limit for 1024 clock cycles and the 3rd step is the full current limit. The TPS65101 has an

extended softstart time where each step is 2048 clock cycles.

All the outputs of the TPS65100/05 have short circuit detection where the device enters shutdown. The

TPS65101, as an exception, does not enter shutdown in case one of the outputs falls below its power good

operational. When the output voltage falls below this threshold again, then the converter continues operation.

condition, then the TPS65100/05 goes into shutdown. Because there is a direct pass from the input to the output

through the diode, the short circuit condition remains. If this condition needs to be avoided, a fuse at the input or

an output disconnect using a single transistor and resistor is required. The negative and positive charge pumps

have an undervoltage lockout to protect the LCD panel of possible latch-up conditions in case of a short circuit

condition or faulty operation. When the negative output voltage is typically above 9.5% of its output voltage

below 8% typ of its output voltage, then the device goes into shutdown as well. See the electrical characteristics

table under fault protection thresholds. The device can be enabled again by toggling the enable pin (EN) below

0.4 V or by cycling the input voltage below the UVLO of 1.7 V. The linear regulator reduces the output current to

typical 20 mA under a short circuit condition when the output voltage is typically < 1 V. See the functional block

diagram. The linear regulator does not go into shutdown under a short-circuit condition.

11

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