AN3240

Operating supply conditions

Doc ID 17689 Rev 1

17/32

5.2

Fixed STHV748 pins on PCB demo

In order to clarify some special pin behavior, a short explanation is given:

EN allows the minimizing of the power consumption. If EN=0, the self-voltage reference is

not supplied. By supplying the reference externally, the total power consumption is reduced.

THSD is a thermal flag. The output stage of the THSD pin is a Nch-MOS open-drain, so it is

necessary to connect the external pull-up resistance (R2

≥10 kΩ) to the positive low-voltage

supply (see Figure 2). If the internal temperature surpasses 160 °C, THSD goes down and

puts all the channels into HZ state. By externally forcing THSD to a positive low-voltage

supply, the thermal protection is disabled.

D_CTR can be used to optimize 2nd HD performance by tuning the fall propagation delay

(TDF - see the datasheet, STHV748; 5-level, ±90 V, 2 A high speed pulser with four

independent channels). If D_CTR is equal to ground, TDF has the nominal value. If D_CTR

is being varied from 2 V to 4.2 V, TDF can be changed from -1 ns to +600 ps, with respect to

the nominal value.

EXPOSED-PAD is internally connected to the substrate. It can be floating or connected to a

100 V capacitance toward ground, in order to reduce noise during the receiving phase. The

fixed configuration of the PCB application pins described is given in Table 8.

Table 8.

Special pin connections

Special pins on the PCB demo

Name

Description

Status on board

EN 64-pin

Enable pin

With EN=1, the IC internally generates the reference

voltages on REF_HVP1/0 (7, 10, 39, 42-pin) and

REF_HVM1/0 (2, 15, 34, 47-pin). These voltages are set

VDDP below HVP and VDDP above HVM, respectively:

REF_HVM# = HVM# + VDDP

REF_HVP# = HVP# - VDDP

When EN=0, it is required that an external voltage is

applied to REF_HVM# and REF_HVP# pins (see the

STHV748 datasheet).

Active – forced to 3 V through

R1=10 k

Ω

THSD 32-pin

Thermal shutdown pin

Active – forced to 3 V through R2=10

k

Ω. The user can monitor the THSD

status on TP1 (test point)

D_CTR 16-pin

Delay control pin

Not active – forced directly to ground

EXPOSED-PAD

Substrate

Not active – connected to ground

through Cs1=0.22 µF